I would like to learn React and therefore trying to build a logfile parser for myself to parse Apache HTTP Logs in CLF format.
However, trying to do this always causes an infinity loop.
import React, { useEffect} from "react";
import logfile from './logfile';
import parse from "clf-parser";
function App() {
const [logContent, setLog] = React.useState([]);
useEffect(()=>{
if(Object.keys(logContent).length === 0){
fetch(logfile)
.then(r => r.text())
.then(text => {
const data = text.split('\n').map(entry => {
return parse(entry);
});
return data;
}).then(
obj => {
console.log(obj);
setLog(obj);
return;
}
);
}
}, [])
return (
<div>
<header><h1>Logfile Parser</h1></header>
<main>{
logContent.map(entry => {
return (<div key={entry.key}>{entry.remote_addr}</div>)
}
)}</main>
</div>
);
}
It's directly related to the setLog(obj);, if I don't use it I have only two entries in my console. Why two and not one though? How to fix this problem?
As M. Elghamry pointed out correct in the comments, the checking for the logContent within the useEffect() was the problem.
After removing the if statement, the loop does not continue happening.
import React, { useEffect} from "react";
import logfile from './logfile';
import parse from "clf-parser";
function App() {
const [logContent, setLog] = React.useState([]);
useEffect(()=>{
fetch(logfile)
.then(r => r.text())
.then(text => {
const data = text.split('\n').map(entry => {
return parse(entry);
});
return data;
}).then(
obj => {
console.log(obj);
setLog(obj);
return;
}
);
}, [])
return (
<div>
<header><h1>Logfile Parser</h1></header>
<main>{
logContent.map(entry => {
return (<div key={entry.key}>{entry.remote_addr}</div>)
}
)}</main>
</div>
);
}
Related
import axios from "axios";
import { useState, useEffect } from "react";
import "./styles.css";
export default function App() {
let [data, setdata] = useState([]);
const update = async () => {
try {
await axios
.get("https://mocki.io/v1/94d0cd81-ed46-4db6-9304-c5e119bcf334")
.then((res) => {
setdata(res.data);
console.log(data);
});
} catch (error) {
console.log(error);
}
};
useEffect(() => {
update();
}, []);
return (
<div className="App">
{data.map((e) => {
return (
<>
<h1>{e.number[0].school}</h1>
</>
);
})}
<button onClick={update}>click me</button>
</div>
);
}
can someone help me so solve this problem, please?
i am trying to display the number's obj, but i cant.
its not the real one, but i make it as similar as the real one.
any help will be appreciated.
thankyou
I've built a code at codesandbox so I could display what is going on.
When I uncomment the <p>{chosenPokemon[0].id}</p> line in the aplication run a error: Cannot read properties of undefined (reading 'id'). Here is the file where the problem is going on:
import { usePokemon } from "../../hooks/usePokemon";
export const MapTest = () => {
const { chosenPokemon } = usePokemon("ditto");
console.log(chosenPokemon);
return (
<>
<h1>Map Test</h1>
{/* <p>{chosenPokemon[0].id}</p> */}
</>
);
};
My conclusion is that my context file is bringing a undefined value before bringing the correct one. Here is my context file:
import { createContext, useContext, useState, useEffect } from "react";
import axios from "axios";
const DittoContext = createContext();
export default function DittoProvider({ children }) {
const [ditto, setDitto] = useState();
const api = axios.create({
baseURL: "https://pokeapi.co/api/v2/pokemon"
});
useEffect(() => {
api
.get("/ditto")
.then((response) => setDitto(response.data))
.catch((err) => console.log(err));
}, []);
return (
<DittoContext.Provider value={{ ditto, setDitto }}>
{children}
</DittoContext.Provider>
);
}
export const useDitto = () => {
const context = useContext(DittoContext);
const { ditto, setDitto } = context;
return { ditto, setDitto };
};
How can I fix this error that has been going on?
I have been trying to get the images from this API to append to the page by mapping through them, but I keep getting one of two error messages saying 'undefined.map is not a function' or 'getBirds.map is not a function.'I've tried leaving the array of objects as it is and setting state to an object and an array(at separate times) but that didn't work. I've also tried using Object.key, Object.values, and Object.entries(each at separate times) to turn the array of objects into an array and then map through my variable and through getBirds(again separately) but those attempts also failed. I have attached three of my attempts below. Can someone help me understand where I've gone wrong?
// Attempt 1
import {useState, useEffect} from 'react'
import axios from 'axios'
function Birds(props) {
const [getBirds, setGetBirds] = useState({})
const {image} = props
useEffect(() => {
async function fetchBirds() {
const URL = `https://audubon-society-api.herokuapp.com/birds`
try {
const res = await axios.get(URL)
console.log(res.data)
setGetBirds(res.data)
} catch (error) {
console.log(error)
}
}
fetchBirds()
}, [])
if (!getBirds) return <h3>Loading...</h3>
return (
<div>
<img src={getBirds.map(image)} alt={getBirds.map(image)}></img>
</div>
)
}
export default Birds
// Attempt 2
import {useState, useEffect} from 'react'
import axios from 'axios'
function Birds(props) {
const [getBirds, setGetBirds] = useState([])
const {image} = props
useEffect(() => {
async function fetchBirds() {
const URL = `https://audubon-society-api.herokuapp.com/birds`
try {
const res = await axios.get(URL)
console.log(res.data)
setGetBirds(res.data)
} catch (error) {
console.log(error)
}
}
fetchBirds()
}, [])
if (!getBirds) return <h3>Loading...</h3>
return (
<div>
<img src={getBirds.map(image)} alt={getBirds.map(image)}></img>
</div>
)
}
export default Birds
// Attempt 3
import {useState, useEffect} from 'react'
import axios from 'axios'
function Birds(props) {
const [getBirds, setGetBirds] = useState({})
const {image} = props
useEffect(() => {
async function fetchBirds() {
const URL = `https://audubon-society-api.herokuapp.com/birds`
try {
const res = await axios.get(URL)
console.log(res.data)
setGetBirds(res.data)
} catch (error) {
console.log(error)
}
}
fetchBirds()
}, [])
const birds = Object.entries(getBirds)
birds.forEach(([key, value]) => {
console.log(key, value)
})
if (!getBirds) return <h3>Loading...</h3>
return (
<div>
<img src={birds.map(image)} alt={birds.map(image)}></img>
</div>
)
}
export default Birds
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.6.3/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.6.3/umd/react-dom.production.min.js"></script>
You would need to initialize your state with an array, so the map function won't get errors, and correct the way you map it:
Initialize state with an array:
const [getBirds, setGetBirds] = useState([]);
Map it:
return (
<div>
{getBirds.map((bird) => (
<img src={bird.image} alt={bird.image}></img>
))}
</div>
);
Also, check your array with length, because [] or {} both equal to true.
if (!getBirds.length) return <h3>Loading...</h3>;
console.log(!![]);
console.log(!!{});
console.log(!![].length)
The completed solution:
import { useState, useEffect } from "react";
import axios from "axios";
function Birds(props) {
const [getBirds, setGetBirds] = useState([]);
useEffect(() => {
async function fetchBirds() {
const URL = 'https://audubon-society-api.herokuapp.com/birds';
try {
const res = await axios.get(URL);
console.log(res.data);
setGetBirds(res.data);
} catch (error) {
console.log(error);
}
}
fetchBirds();
}, []);
if (!getBirds.length) return <h3>Loading...</h3>;
return (
<div>
{getBirds.map((bird) => (
<img src={bird.image} alt={bird.image}></img>
))}
</div>
);
}
export default Birds;
Working Example:
Your init state of birds and setBirds should be an array [] not an object {}, also you don't need:
const birds = Object.entries(getBirds). fetch return array of birds already.
<img src={birds.map(image)} alt={birds.map(image)}></img> is wrong, the array loop map should render an image for each bird.
Below code will run for your need:
import React, {useState, useEffect} from "react";
import axios from 'axios';
function Birds(props) {
//- const [getBirds, setGetBirds] = useState([])
//- const {image} = props
// +
const [birds, setGetBirds] = useState([])
useEffect(() => {
async function fetchBirds() {
const URL = `https://audubon-society-api.herokuapp.com/birds`
try {
const res = await axios.get(URL)
console.log(res.data)
setGetBirds(res.data)
} catch (error) {
console.log(error)
}
}
fetchBirds()
}, [])
// - const birds = Object.entries(getBirds)
// - birds.forEach(([key, value]) => {
// - console.log(key, value)
// - })
// - if (!getBirds) return <h3>Loading...</h3>
if (!birds) return <h3>Loading...</h3>
return (
<div>
{/* <img src={birds.map(image)} alt={birds.map(image)}></img> */}
{birds.map((item, index) =>
<img src={item.image} alt={index}></img>
)}
</div>
)
}
export default Birds
I'm trying to make a page to show the details of each video.
I fetched multiple video data from the back-end and stored them as global state.
This code works if I go to the page through the link inside the app. But If I reload or open the URL directory from the browser, It can not load the single video data.
How should I do to make this work?
Thanx
Single Video Page
import { useState, useEffect, useContext } from "react";
import { useParams } from "react-router-dom";
import { VideoContext } from "../context/videoContext";
const SingleVideo = () => {
let { slug } = useParams();
const [videos, setVideos] = useContext(VideoContext);
const [video, setVideo] = useState([]);
useEffect(() => {
const result = videos.find((videos) => {
return videos.uuid === slug;
});
setVideo((video) => result);
}, []);
return (
<>
<div>
<h1>{video.title}</h1>
<p>{video.content}</p>
<img src={video.thumbnail} alt="" />
</div>
</>
);
};
export default SingleVideo;
Context
import React, { useState, createContext, useEffect } from "react";
import Axios from "axios";
import { AxiosResponse } from "axios";
export const VideoContext = createContext();
export const VideoProvider = (props) => {
const [videos, setVideos] = useState([]);
const config = {
headers: { "Access-Control-Allow-Origin": "*" },
};
useEffect(() => {
//Fetch Vidoes
Axios.get(`http://localhost:5000/videos`, config)
.then((res: AxiosResponse) => {
setVideos(res.data);
})
.catch((err) => {
console.log(err);
});
}, []);
return (
<VideoContext.Provider value={[videos, setVideos]}>
{props.children}
</VideoContext.Provider>
);
};
I think the reason is because when you refresh the app, you fetch the video data on context and the useEffect on your single video page component runs before you receive those data.
To fix you can simply modify slightly your useEffect in your single video component to update whenever you receive those data:
useEffect(() => {
if (videos.length) {
const result = videos.find((videos) => {
return videos.uuid === slug;
});
setVideo((video) => result);
}
}, [videos]);
I thought had a better grasp of hooks but I've clearly got something wrong here. Not all of the character objects will have what I'm trying to get but it wont work with those that do.
I cna't even build in a check for character.comics.available. Same errors appear. I'm presuming I'm getting them before the state is set? But {character.name} always works.
CharacterDetail.js
import React from "react";
import { useParams } from "react-router-dom";
import useCharacter from "../hooks/useCharacter";
const CharacterDetail = () => {
// from the Route path="/character/:id"
const { id } = useParams();
// custom hook. useCharacter.js
const [character] = useCharacter(id);
// this only works sometimes but errors if i refresh the page
// console.log(character.comics.available);
return (
<div>
<h2 className="ui header">Character Details</h2>
<p>Works every time: {character.name}</p>
<div className="ui segment"></div>
<pre></pre>
</div>
);
};
export default CharacterDetail;
Custom hook useCharacter.js
import { useState, useEffect } from "react";
import marvel from "../apis/marvel";
const useCharacter = (id) => {
const [character, setCharacter] = useState({});
useEffect(() => {
loadItem();
return () => {};
}, [id]);
const loadItem = async (term) => {
const response = await marvel.get(`/characters/${id}`);
console.log(response.data.data.results[0]);
setCharacter(response.data.data.results[0]);
};
return [character];
};
export default useCharacter;
error when console is uncommented
Uncaught TypeError: Cannot read property 'available' of undefined
at CharacterDetail (CharacterDetail.js:11)
...
Here is the character object.
thanks to #Nikita for the pointers. Settled on this...
CharacterDetail.js
import React from "react";
import { useParams } from "react-router-dom";
import useCharacter from "../hooks/useCharacter";
const CharacterDetail = () => {
const { id } = useParams();
// custom hook. useCharacter.js
const { isLoading, character } = useCharacter(id);
const isArray = character instanceof Array;
if (!isLoading && isArray === false) {
console.log("isLoading", isArray);
const thumb =
character.thumbnail.path +
"/portrait_uncanny." +
character.thumbnail.extension;
return (
<div>
<h2 className="ui header">{character.name}</h2>
<img src={thumb} />
<div className="ui segment">{character.comics.available}</div>
<div className="ui segment">{character.series.available}</div>
<div className="ui segment">{character.stories.available}</div>
</div>
);
}
return <div>Loading...</div>;
};
export default CharacterDetail;
useCharacter.js
import { useState, useEffect } from "react";
import marvel from "../apis/marvel";
function useCharacter(id) {
const [character, setCharacter] = useState([]);
const [isLoading, setIsLoading] = useState(false);
useEffect(() => {
setIsLoading(true);
const fetchData = async () => {
setIsLoading(true);
await marvel
.get(`/characters/${id}`)
.then((response) => {
/* DO STUFF WHEN THE CALLS SUCCEEDS */
setIsLoading(false);
setCharacter(response.data.data.results[0]);
})
.catch((e) => {
/* HANDLE THE ERROR (e) */
});
};
fetchData();
}, [id]);
return {
isLoading,
character,
};
}
export default useCharacter;