hi i have an issue with set state , i write the function that i get Position x,y and size of width , height(That is the name of the state that holds them POx1, POY1, widthSize, heightSize) and depend on user choise, i change the state's that user get to me and Use them. but after the first setSate for all these State i can't update and or change them . these are my code's:
function DrawPicture() { // this function call after click
setCountClick(CountClick + 1);
var Se_image = new Image();
Se_image.src = ImgSRC;// (ImgSRC) is the State i define it before
Se_image.onload = function () {
ctxRef.current.globalCompositeOperation = "source-over";
if (CountClick === 2) {// For some reason, I want this condition to be executed after calling the above function twice
var img = Se_image
PictureCategory(img) // This function is shown below
var canvas = canvasRef.current
var ctx = canvas.getContext('2d');
var imageData = ctx.getImageData(POx1, POY1, widthSize, heightSize);
var data = imageData.data;
console.log(lineColor);
const r = parseInt(lineColor.substr(1, 2), 16)
const g = parseInt(lineColor.substr(3, 2), 16)
const b = parseInt(lineColor.substr(5, 2), 16)
var changeColor = function () {
for (var i = 0; i < data.length; i += 4) {
data[i] = r
data[i + 1] = g
data[i + 2] = b
}
ctx.putImageData(imageData, POx1, POY1);
};
changeColor();
setCountClick(1);
setPointer(false);
}
}
}
and this is my PictureCategory() function:
For convenience, I only took one of the modes
function PictureCategory(image) {
switch (PictureTopic) {
case "Girl":
const XG = POx1 - (0.5 * widthSize) < 0 ? 0 : POx1 - (0.5 * widthSize);
const newWidth= 2.4*widthSize;
const newheight= 2.5*widthSize;
setPOx1(XG)
setwidthSize(newWidth)
setheightSize(newheight)
ctxRef.current.clearRect(XG, POY1, newWidth, newheight);
ctxRef.current.drawImage(image, XG, POY1, 2.4 * widthSize, 2.5 * heightSize);
break;
default:
ctxRef.current.drawImage(image, POx1, POY1, widthSize, heightSize);
break;
}
}
i want to change state's with above function please help me !!!
Not sure if it'll fix your issue, but the following has to be done in any case.
It should be
setCountClick(countClick=> countClick + 1);
When state is updated using its previous value, the callback argument of the state setter should be used.
See https://reactjs.org/docs/state-and-lifecycle.html#state-updates-may-be-asynchronous
i know it's not your answer for this question. but you can use this codes for have new value .
I stored the new values in an object and returned them:
function DrawPicture() {
setCountClick(CountClick + 1);
var Se_image = new Image();
Se_image.src = ImgSRC;
Se_image.onload = function () {
ctxRef.current.globalCompositeOperation = "source-over";
if (CountClick === 2) {
var img = Se_image
const Sizes =PictureCategory(img) // you can store new value in valible
var canvas = canvasRef.current
var ctx = canvas.getContext('2d');
var imageData = ctx.getImageData(Sizes[0].x, Sizes[0].y, Sizes[0].width, Sizes[0].height);
var data = imageData.data;
console.log(lineColor);
const r = parseInt(lineColor.substr(1, 2), 16)
const g = parseInt(lineColor.substr(3, 2), 16)
const b = parseInt(lineColor.substr(5, 2), 16)
var changeColor = function () {
for (var i = 0; i < data.length; i += 4) {
data[i] = r
data[i + 1] = g
data[i + 2] = b
}
ctx.putImageData(imageData,Sizes[0].x, Sizes[0].y);
};
changeColor();
setCountClick(1);
setPointer(false);
}
}
}
function PictureCategory(image) {
switch (PictureTopic) {
case "Girl":
const XG = POx1 - (0.5 * widthSize) < 0 ? 0 : POx1 - (0.5 * widthSize);
const newWidth= 2.4*widthSize;
const newheight= 2.5*widthSize;
ctxRef.current.clearRect(XG, POY1, newWidth, newheight);
ctxRef.current.drawImage(image, XG, POY1, 2.4 * widthSize, 2.5 * heightSize);
return[{x: XG,y:POY1,width:newWidth,height:newheight}]
default:
ctxRef.current.drawImage(image, POx1, POY1, widthSize, heightSize);
break;
}
}
My issue is returning the values saved in a database to the form in each cell in the range. The saveToDB script below is able to save the values from the form to the database, but I don't know how to retrieve those values. Hope you could help me. Thanks so much!
Form: sample form
Database: database sample
function saveToDB(){
range = ["C2","C4","C6"]
var newRange = range.map(f => formSheet.getRange(f).getValue())
dbSheet.appendRow(newRange)
}
function loadToForm(){
range = ["C2","C4","C6"]
var dbArray = dbSheet.getRange(2,1,dbSheet.getLastRow(),dbSheet.getLastColumn()).getValues()
var newArray = dbArray.filter(function(row){
if(row[0] === "Fred" && row[0] !== -1){
return row !== ""
}
})
//Don't know how to return each value to each cell in the range
//Update - this is the code that did it
range.map((f,i) => formSheet.getRange(f).setValue(newArray[0][i]))
}
function saveToDB() {
const ss = SpreadsheetApp.getActive();
const fsh = ss.getSheetByName('Form Sheet Name');
const dsh = ss.getSheetByName('Database Sheet Name')
let arr = ["C2", "C4", "C6"].map(e => fsh.getRange(e).getValue());
dsh.appendRow(arr);
}
function loadToForm() {
const range = ["C2", "C4", "C6"];
const ss = SpreadsheetApp.getActive();
const dsh = ss.getSheetByName('Database Sheet Name');
const fsh = ss.getSheetByName('Form Sheet Name');
let r = SpreadsheetApp.getUi().prompt('Row Number','Enter Row Number', SpreadsheetApp.getUi().ButtonSet.OK_CANCEL);
if(r.getSelectedButton() == SpreadsheetApp.getUi().Button.OK) {
let vs = dsh.getRange(row, 1, 1, dsh.getLastColumn()).getValues()[0];
range.forEach((e,i) => { fsh.getRange(e).setValue(vs[i])
});
}
}
All you have to do is use the setValue() function and iterate through each cell like so:
function loadToForm(){
range = ["C2","C4","C6"]
var dbArray = dbSheet.getRange(2,1,dbSheet.getLastRow(),dbSheet.getLastColumn()).getValues()
var newArray = dbArray.filter(function(row){
if(row[0] === "Fred" && row[0] !== -1){
return row !== ""
}
})
//Remove useless extra dimension from array
newArray = newArray[0];
//Solution 1 using RangeList
var ranges = formSheet.getRangeList(range).getRanges();
for(var i in newArray){
ranges[i].setValue(newArray[i]);
}
//Solution 2 not using RangeList
for(var i in newArray){
formSheet.getRange(range[i]).setValue(newArray[i]);
}
}
I am trying to achieve a method in which the array steps got filled with new data every time I click on the button of Create New array, but instead of that, the data is getting appended instead of updating.
here are my states :
const [arr , setArray] = useState(createArray())
const [steps , setSteps] = useState([]);
const [selectedAlgorithm , setSelectedAlgorithm] = useState ();
here is my create new Array function :
const handleCreateNewData = ()=>{
let newarr = createArray();
setArray ([]);
setArray([...newarr]);
setSteps ([]);
setTimeout(()=>{
if ( algorithms[selectedAlgorithm] !== undefined){
algorithms[selectedAlgorithm](arr, steps , setSteps);
console.log('running')
}
},2000)
}
here is my bubble sort algorithm :
export const BubbleSort = (array , steps ,setSteps) =>{
let funarray = new Array();
funarray = [...array] ;
for (let i = 0 ; i < funarray.length-1 ; i++){
for(let j = 0 ; j < funarray.length-1 ; j++){
if(funarray[j]>funarray[j+1]){
[funarray[j],funarray[j+1]] = [funarray[j+1],funarray[j]]
setSteps([...steps, funarray])
steps.push(funarray.slice());
console.log('Working')
}
}
}
return funarray;
}
What is supposed to do is every time I click on create new array it should generate a new set of arrays but instead of creating new arrays it just appending the new arrays in the old steps.
You can create a temp array to hold the steps, then when the loops are done, call setSteps:
const BubbleSort = (array, steps, setSteps) => {
let funarray = [];
funarray = [...array];
let temp = [];
for (let i = 0; i < funarray.length - 1; i++) {
for (let j = 0; j < funarray.length - 1; j++) {
if (funarray[j] > funarray[j + 1]) {
[funarray[j], funarray[j + 1]] = [funarray[j + 1], funarray[j]];
temp.push(funarray)
}
}
}
setSteps(temp);
return funarray;
};
Sample: https://codesandbox.io/s/cool-wind-ijj7z?file=/src/App.js
I have Base64-encoded binary data in a string:
const contentType = 'image/png';
const b64Data = 'iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==';
I would like to create a blob: URL containing this data and display it to the user:
const blob = new Blob(????, {type: contentType});
const blobUrl = URL.createObjectURL(blob);
window.location = blobUrl;
I haven't been been able to figure out how to create the BLOB.
In some cases I am able to avoid this by using a data: URL instead:
const dataUrl = `data:${contentType};base64,${b64Data}`;
window.location = dataUrl;
However, in most cases the data: URLs are prohibitively large.
How can I decode a Base64 string to a BLOB object in JavaScript?
The atob function will decode a Base64-encoded string into a new string with a character for each byte of the binary data.
const byteCharacters = atob(b64Data);
Each character's code point (charCode) will be the value of the byte. We can create an array of byte values by applying this using the .charCodeAt method for each character in the string.
const byteNumbers = new Array(byteCharacters.length);
for (let i = 0; i < byteCharacters.length; i++) {
byteNumbers[i] = byteCharacters.charCodeAt(i);
}
You can convert this array of byte values into a real typed byte array by passing it to the Uint8Array constructor.
const byteArray = new Uint8Array(byteNumbers);
This in turn can be converted to a BLOB by wrapping it in an array and passing it to the Blob constructor.
const blob = new Blob([byteArray], {type: contentType});
The code above works. However the performance can be improved a little by processing the byteCharacters in smaller slices, rather than all at once. In my rough testing 512 bytes seems to be a good slice size. This gives us the following function.
const b64toBlob = (b64Data, contentType='', sliceSize=512) => {
const byteCharacters = atob(b64Data);
const byteArrays = [];
for (let offset = 0; offset < byteCharacters.length; offset += sliceSize) {
const slice = byteCharacters.slice(offset, offset + sliceSize);
const byteNumbers = new Array(slice.length);
for (let i = 0; i < slice.length; i++) {
byteNumbers[i] = slice.charCodeAt(i);
}
const byteArray = new Uint8Array(byteNumbers);
byteArrays.push(byteArray);
}
const blob = new Blob(byteArrays, {type: contentType});
return blob;
}
const blob = b64toBlob(b64Data, contentType);
const blobUrl = URL.createObjectURL(blob);
window.location = blobUrl;
Full Example:
const b64toBlob = (b64Data, contentType='', sliceSize=512) => {
const byteCharacters = atob(b64Data);
const byteArrays = [];
for (let offset = 0; offset < byteCharacters.length; offset += sliceSize) {
const slice = byteCharacters.slice(offset, offset + sliceSize);
const byteNumbers = new Array(slice.length);
for (let i = 0; i < slice.length; i++) {
byteNumbers[i] = slice.charCodeAt(i);
}
const byteArray = new Uint8Array(byteNumbers);
byteArrays.push(byteArray);
}
const blob = new Blob(byteArrays, {type: contentType});
return blob;
}
const contentType = 'image/png';
const b64Data = 'iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==';
const blob = b64toBlob(b64Data, contentType);
const blobUrl = URL.createObjectURL(blob);
const img = document.createElement('img');
img.src = blobUrl;
document.body.appendChild(img);
Here is a more minimal method without any dependencies or libraries.
It requires the new fetch API. (Can I use it?)
var url = "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg=="
fetch(url)
.then(res => res.blob())
.then(console.log)
With this method you can also easily get a ReadableStream, ArrayBuffer, text, and JSON.
(fyi this also works with node-fetch in Node)
As a function:
const b64toBlob = (base64, type = 'application/octet-stream') =>
fetch(`data:${type};base64,${base64}`).then(res => res.blob())
But I would encourage you to don't use base64 in the first place. There are better ways to send and receive binary data. JSON isn't always the best option. it takes up more bandwidth and waste processing time (de)encodeing stuff. Us eg canvas.toBlob instead of canvas.toDataURL and use FormData to send binary files. you can also return back a multipart payload and decode it using await response.formData() that is coming from a server response. FormData can go both ways.
I did a simple performance test towards Jeremy's ES6 sync version.
The sync version will block UI for a while.
keeping the devtool open can slow the fetch performance
document.body.innerHTML += '<input autofocus placeholder="try writing">'
// get some dummy gradient image
var img=function(){var a=document.createElement("canvas"),b=a.getContext("2d"),c=b.createLinearGradient(0,0,1500,1500);a.width=a.height=3000;c.addColorStop(0,"red");c.addColorStop(1,"blue");b.fillStyle=c;b.fillRect(0,0,a.width,a.height);return a.toDataURL()}();
async function perf() {
const blob = await fetch(img).then(res => res.blob())
// turn it to a dataURI
const url = img
const b64Data = url.split(',')[1]
// Jeremy Banks solution
const b64toBlob = (b64Data, contentType = '', sliceSize=512) => {
const byteCharacters = atob(b64Data);
const byteArrays = [];
for (let offset = 0; offset < byteCharacters.length; offset += sliceSize) {
const slice = byteCharacters.slice(offset, offset + sliceSize);
const byteNumbers = new Array(slice.length);
for (let i = 0; i < slice.length; i++) {
byteNumbers[i] = slice.charCodeAt(i);
}
const byteArray = new Uint8Array(byteNumbers);
byteArrays.push(byteArray);
}
const blob = new Blob(byteArrays, {type: contentType});
return blob;
}
// bench blocking method
let i = 500
console.time('blocking b64')
while (i--) {
await b64toBlob(b64Data)
}
console.timeEnd('blocking b64')
// bench non blocking
i = 500
// so that the function is not reconstructed each time
const toBlob = res => res.blob()
console.time('fetch')
while (i--) {
await fetch(url).then(toBlob)
}
console.timeEnd('fetch')
console.log('done')
}
perf()
Optimized (but less readable) implementation:
function base64toBlob(base64Data, contentType) {
contentType = contentType || '';
var sliceSize = 1024;
var byteCharacters = atob(base64Data);
var bytesLength = byteCharacters.length;
var slicesCount = Math.ceil(bytesLength / sliceSize);
var byteArrays = new Array(slicesCount);
for (var sliceIndex = 0; sliceIndex < slicesCount; ++sliceIndex) {
var begin = sliceIndex * sliceSize;
var end = Math.min(begin + sliceSize, bytesLength);
var bytes = new Array(end - begin);
for (var offset = begin, i = 0; offset < end; ++i, ++offset) {
bytes[i] = byteCharacters[offset].charCodeAt(0);
}
byteArrays[sliceIndex] = new Uint8Array(bytes);
}
return new Blob(byteArrays, { type: contentType });
}
Following is my TypeScript code which can be converted easily into JavaScript and you can use
/**
* Convert BASE64 to BLOB
* #param base64Image Pass Base64 image data to convert into the BLOB
*/
private convertBase64ToBlob(base64Image: string) {
// Split into two parts
const parts = base64Image.split(';base64,');
// Hold the content type
const imageType = parts[0].split(':')[1];
// Decode Base64 string
const decodedData = window.atob(parts[1]);
// Create UNIT8ARRAY of size same as row data length
const uInt8Array = new Uint8Array(decodedData.length);
// Insert all character code into uInt8Array
for (let i = 0; i < decodedData.length; ++i) {
uInt8Array[i] = decodedData.charCodeAt(i);
}
// Return BLOB image after conversion
return new Blob([uInt8Array], { type: imageType });
}
See this example: https://jsfiddle.net/pqhdce2L/
function b64toBlob(b64Data, contentType, sliceSize) {
contentType = contentType || '';
sliceSize = sliceSize || 512;
var byteCharacters = atob(b64Data);
var byteArrays = [];
for (var offset = 0; offset < byteCharacters.length; offset += sliceSize) {
var slice = byteCharacters.slice(offset, offset + sliceSize);
var byteNumbers = new Array(slice.length);
for (var i = 0; i < slice.length; i++) {
byteNumbers[i] = slice.charCodeAt(i);
}
var byteArray = new Uint8Array(byteNumbers);
byteArrays.push(byteArray);
}
var blob = new Blob(byteArrays, {type: contentType});
return blob;
}
var contentType = 'image/png';
var b64Data = Your Base64 encode;
var blob = b64toBlob(b64Data, contentType);
var blobUrl = URL.createObjectURL(blob);
var img = document.createElement('img');
img.src = blobUrl;
document.body.appendChild(img);
For all browser support, especially on Android, perhaps you can add this:
try{
blob = new Blob(byteArrays, {type : contentType});
}
catch(e){
// TypeError old Google Chrome and Firefox
window.BlobBuilder = window.BlobBuilder ||
window.WebKitBlobBuilder ||
window.MozBlobBuilder ||
window.MSBlobBuilder;
if(e.name == 'TypeError' && window.BlobBuilder){
var bb = new BlobBuilder();
bb.append(byteArrays);
blob = bb.getBlob(contentType);
}
else if(e.name == "InvalidStateError"){
// InvalidStateError (tested on FF13 WinXP)
blob = new Blob(byteArrays, {type : contentType});
}
else{
// We're screwed, blob constructor unsupported entirely
}
}
For all copy-paste lovers out there like me, here is a cooked download function which works on Chrome, Firefox and Edge:
window.saveFile = function (bytesBase64, mimeType, fileName) {
var fileUrl = "data:" + mimeType + ";base64," + bytesBase64;
fetch(fileUrl)
.then(response => response.blob())
.then(blob => {
var link = window.document.createElement("a");
link.href = window.URL.createObjectURL(blob, { type: mimeType });
link.download = fileName;
document.body.appendChild(link);
link.click();
document.body.removeChild(link);
});
}
I'm posting a more declarative way of sync Base64 converting. While async fetch().blob() is very neat and I like this solution a lot, it doesn't work on Internet Explorer 11 (and probably Edge - I haven't tested this one), even with the polyfill - take a look at my comment to Endless' post for more details.
const blobPdfFromBase64String = base64String => {
const byteArray = Uint8Array.from(
atob(base64String)
.split('')
.map(char => char.charCodeAt(0))
);
return new Blob([byteArray], { type: 'application/pdf' });
};
Bonus
If you want to print it you could do something like:
const isIE11 = !!(window.navigator && window.navigator.msSaveOrOpenBlob); // Or however you want to check it
const printPDF = blob => {
try {
isIE11
? window.navigator.msSaveOrOpenBlob(blob, 'documents.pdf')
: printJS(URL.createObjectURL(blob)); // http://printjs.crabbly.com/
} catch (e) {
throw PDFError;
}
};
Bonus x 2 - Opening a BLOB file in new tab for Internet Explorer 11
If you're able to do some preprocessing of the Base64 string on the server you could expose it under some URL and use the link in printJS :)
For image data, I find it simpler to use canvas.toBlob (asynchronous)
function b64toBlob(b64, onsuccess, onerror) {
var img = new Image();
img.onerror = onerror;
img.onload = function onload() {
var canvas = document.createElement('canvas');
canvas.width = img.width;
canvas.height = img.height;
var ctx = canvas.getContext('2d');
ctx.drawImage(img, 0, 0, canvas.width, canvas.height);
canvas.toBlob(onsuccess);
};
img.src = b64;
}
var base64Data = 'data:image/jpg;base64,/9j/4AAQSkZJRgABAQA...';
b64toBlob(base64Data,
function(blob) {
var url = window.URL.createObjectURL(blob);
// do something with url
}, function(error) {
// handle error
});
If you can stand adding one dependency to your project there's the great blob-util npm package that provides a handy base64StringToBlob function. Once added to your package.json you can use it like this:
import { base64StringToBlob } from 'blob-util';
const contentType = 'image/png';
const b64Data = 'iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==';
const blob = base64StringToBlob(b64Data, contentType);
// Do whatever you need with your blob...
I noticed that Internet Explorer 11 gets incredibly slow when slicing the data like Jeremy suggested. This is true for Chrome, but Internet Explorer seems to have a problem when passing the sliced data to the Blob-Constructor. On my machine, passing 5 MB of data makes Internet Explorer crash and memory consumption is going through the roof. Chrome creates the blob in no time.
Run this code for a comparison:
var byteArrays = [],
megaBytes = 2,
byteArray = new Uint8Array(megaBytes*1024*1024),
block,
blobSlowOnIE, blobFastOnIE,
i;
for (i = 0; i < (megaBytes*1024); i++) {
block = new Uint8Array(1024);
byteArrays.push(block);
}
//debugger;
console.profile("No Slices");
blobSlowOnIE = new Blob(byteArrays, { type: 'text/plain'});
console.profileEnd();
console.profile("Slices");
blobFastOnIE = new Blob([byteArray], { type: 'text/plain'});
console.profileEnd();
So I decided to include both methods described by Jeremy in one function. Credits go to him for this.
function base64toBlob(base64Data, contentType, sliceSize) {
var byteCharacters,
byteArray,
byteNumbers,
blobData,
blob;
contentType = contentType || '';
byteCharacters = atob(base64Data);
// Get BLOB data sliced or not
blobData = sliceSize ? getBlobDataSliced() : getBlobDataAtOnce();
blob = new Blob(blobData, { type: contentType });
return blob;
/*
* Get BLOB data in one slice.
* => Fast in Internet Explorer on new Blob(...)
*/
function getBlobDataAtOnce() {
byteNumbers = new Array(byteCharacters.length);
for (var i = 0; i < byteCharacters.length; i++) {
byteNumbers[i] = byteCharacters.charCodeAt(i);
}
byteArray = new Uint8Array(byteNumbers);
return [byteArray];
}
/*
* Get BLOB data in multiple slices.
* => Slow in Internet Explorer on new Blob(...)
*/
function getBlobDataSliced() {
var slice,
byteArrays = [];
for (var offset = 0; offset < byteCharacters.length; offset += sliceSize) {
slice = byteCharacters.slice(offset, offset + sliceSize);
byteNumbers = new Array(slice.length);
for (var i = 0; i < slice.length; i++) {
byteNumbers[i] = slice.charCodeAt(i);
}
byteArray = new Uint8Array(byteNumbers);
// Add slice
byteArrays.push(byteArray);
}
return byteArrays;
}
}
The method with fetch is the best solution, but if anyone needs to use a method without fetch then here it is, as the ones mentioned previously didn't work for me:
function makeblob(dataURL) {
const BASE64_MARKER = ';base64,';
const parts = dataURL.split(BASE64_MARKER);
const contentType = parts[0].split(':')[1];
const raw = window.atob(parts[1]);
const rawLength = raw.length;
const uInt8Array = new Uint8Array(rawLength);
for (let i = 0; i < rawLength; ++i) {
uInt8Array[i] = raw.charCodeAt(i);
}
return new Blob([uInt8Array], { type: contentType });
}
In browser just
Uint8Array.from(atob(YOUR_BASE64_DATA), (c) => c.charCodeAt(0))
compare with fetch
!(async () => {
const start = performance.now();
let i = 0;
while (i++ < 1e3) {
const dataUrl =
"data:application/octet-stream;base64,H4sIAAAAAAAAA0vOzyvOz0nVy8lP10jISM3JyVdIr8osUFCpdkksSdXLyy/X0KxN0ORKHlU3qm5U3ai6UXWj6kauOgBVt1KRLwcAAA==";
body = await (await fetch(dataUrl)).blob();
}
console.log(performance.now() - start); // 508.19999999925494ms
})();
!(async () => {
const start = performance.now();
let i = 0;
while (i++ < 1e3) {
const base64Data =
"H4sIAAAAAAAAA0vOzyvOz0nVy8lP10jISM3JyVdIr8osUFCpdkksSdXLyy/X0KxN0ORKHlU3qm5U3ai6UXWj6kauOgBVt1KRLwcAAA==";
body = Uint8Array.from(atob(base64Data), (c) => c.charCodeAt(0));
}
console.log(performance.now() - start); // 7.899999998509884ms
})();
Depends on your data size, choose performance one.
Two different variations
function base64ToBlob(base64, contentType='image/png', chunkLength=512) {
const byteCharsArray = Array.from(atob(base64.substr(base64.indexOf(',') + 1)));
const chunksIterator = new Array(Math.ceil(byteCharsArray.length / chunkLength));
const bytesArrays = [];
for (let c = 0; c < chunksIterator.length; c++) {
bytesArrays.push(new Uint8Array(byteCharsArray.slice(c * chunkLength, chunkLength * (c + 1)).map(s => s.charCodeAt(0))));
}
const blob = new Blob(bytesArrays, {type: contentType});
return blob;
}
/* Not sure how it performs with big images */
async function base64ToBlobLight(base64) { return await fetch(base64).then(res => res.blob()); }
/* Test */
const base64Data = 'data:image/png;base64,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';
const blob = base64ToBlob(base64Data);
const blobUrl = URL.createObjectURL(blob);
const img = document.createElement('img');
img.src = blobUrl;
document.body.appendChild(img);
/**********************/
/* Test */
(async () => {
const blob = await base64ToBlobLight(base64Data);
const blobUrl = URL.createObjectURL(blob);
const img = document.createElement('img');
img.src = blobUrl;
document.body.appendChild(img);
})();
This would prove to be much short solution.
const byteArray = new Buffer(base64String.replace(/^[\w\d;:\/]+base64\,/g, ''), 'base64');
base64String is the string containing the base 64 string.
byteArray is the array you need.
The regex replacement is optional and is just there to deal with prefix as in the case of dataurl string.
I am doing my project in reactjs and i want time ago to show in table.i am using moment js to show time ago(fromNow()) but it shows the time few second only when the data comes from server.And it shows directly 6hrs ago if the data are not coming from server.Eg afer 2minutes of time interval it shows 6 hours ago.As shown in table below.
the code of my project is shown below
componentDidMount() {
let socket = new WebSocket('wss://api.example.com.np/ws');
this.setState({ socket: socket,noOfVehicle:this.state.supportInfo.length });
this.getSupportInfo();
socket.onmessage = ((message) => {
let socketData = JSON.parse(message.data);
let device_id = socketData[0].device_id;
let updatedSupportInfo = this.getUpdatedInfo(this.state.sourceName);
let flag = true;
let uSupport = updatedSupportInfo.map(function(item){
if(device_id == item.device_id){
item.current_pos = socketData[0].current_pos;
if(item.current_pos){
flag = true;
item["latlng"] = item.current_pos.x + ',' + item.current_pos.y;
}else{
flag = false;
}
let time = new Date(socketData[0].timestamp);
let now = new Date();
let timeAgoIn = moment(time).fromNow(true);
item["timeAgoIn"] = timeAgoIn;
}
getSupportInfo() {
axios({
method: 'get',
url: 'https://support.taranga.com.np/support_info'
})
.then((response) => {
for (var i = 0; i < response.data.length; i++) {
if(response.data[i].current_pos){
response.data[i]["latlng"] = response.data[i].current_pos.x + ',' + response.data[i].current_pos.y;
let time = new Date(response.data[i].timestamp)
let now = new Date();
let a = moment(time);
let b = moment(now);
let timeAgo = b.diff(a, 'hours')
let timeAgoIn = moment(time).fromNow(true)
response.data[i]["timeAgo"] = timeAgo;
response.data[i]["timeAgoIn"] = timeAgoIn;
}
}
this.setState({
supportInfo: response.data
});
})
.catch((error)=>{
throw (error);
});
}
getUpdatedInfo(name) {
let uInfo = [];
let tempSupport = this.state.supportInfo.slice();
_.map(tempSupport,(value,key) =>{
if(value.timeAgo !=0){
let time = new Date(value.timestamp)
let now = new Date();
let a = moment(time);
let b = moment(now);
let timeAgo = b.diff(a, 'minutes')
console.log(timeAgo);
//let timeAgo = moment.duration(b-a).humanize()
let timeAgoIn = moment(time).fromNow(true)
value["timeAgo"] = timeAgo;
value["timeAgoIn"] = timeAgoIn;
}
});
this.setState({
supportInfo:tempSupport
});
the code to show in table is
<TableHeaderColumn dataField="timeAgoIn" dataSort={true}>Time Ago</TableHeaderColumn>
I believe your logic is flawed, when you get the info you are storing the timeAgo once, however timeAgo is a property that changes over time, ex:
You receive a message at 12:00, you set timeAgo to 1 second (or w/e js sets it to)
You check your screen at 12:05, timeAgo for that message is still 1 second, because this is calculated once, but time has passed and timeAgo should be 5 seconds ago, right?
timeAgo property should remain as the timestamp you received from server and be calculated when you refresh your table (when you want to do this is a different topic)