I have recently moved from Angular to ReactJs. I am using jQuery for API calls. I have an API which returns a random user list that is to be printed in a list.
I am not sure how to write my API calls. What is best practice for this?
I tried the following but I am not getting any output. I am open to implementing alternative API libraries if necessary.
Below is my code:
import React from 'react';
export default class UserList extends React.Component {
constructor(props) {
super(props);
this.state = {
person: []
};
}
UserList(){
return $.getJSON('https://randomuser.me/api/')
.then(function(data) {
return data.results;
});
}
render() {
this.UserList().then(function(res){
this.state = {person: res};
});
return (
<div id="layout-content" className="layout-content-wrapper">
<div className="panel-list">
{this.state.person.map((item, i) =>{
return(
<h1>{item.name.first}</h1>
<span>{item.cell}, {item.email}</span>
)
})}
<div>
</div>
)
}
}
In this case, you can do ajax call inside componentDidMount, and then update state
export default class UserList extends React.Component {
constructor(props) {
super(props);
this.state = {person: []};
}
componentDidMount() {
this.UserList();
}
UserList() {
$.getJSON('https://randomuser.me/api/')
.then(({ results }) => this.setState({ person: results }));
}
render() {
const persons = this.state.person.map((item, i) => (
<div>
<h1>{ item.name.first }</h1>
<span>{ item.cell }, { item.email }</span>
</div>
));
return (
<div id="layout-content" className="layout-content-wrapper">
<div className="panel-list">{ persons }</div>
</div>
);
}
}
You may want to check out the Flux Architecture. I also recommend checking out React-Redux Implementation. Put your api calls in your actions. It is much more cleaner than putting it all in the component.
Actions are sort of helper methods that you can call to change your application state or do api calls.
Use fetch method inside componentDidMount to update state:
componentDidMount(){
fetch('https://randomuser.me/api/')
.then(({ results }) => this.setState({ person: results }));
}
This discussion has been for a while and #Alexander T.'s answer provided a good guide to follow for newer of React like me. And I'm going to share some additional know-how about calling the same API multiple times to refresh the component, I think it's probably a common question for beginners.
componentWillReceiveProps(nextProps), from official documentation :
If you need to update the state in response to prop changes (for
example, to reset it), you may compare this.props and nextProps and
perform state transitions using this.setState() in this method.
We could conclude that here is the place we handle props from the parent component, have API calls, and update the state.
Base on #Alexander T.'s example:
export default class UserList extends React.Component {
constructor(props) {
super(props);
this.state = {person: []};
}
componentDidMount() {
//For our first load.
this.UserList(this.props.group); //maybe something like "groupOne"
}
componentWillReceiveProps(nextProps) {
// Assuming parameter comes from url.
// let group = window.location.toString().split("/")[*indexParameterLocated*];
// this.UserList(group);
// Assuming parameter comes from props that from parent component.
let group = nextProps.group; // Maybe something like "groupTwo"
this.UserList(group);
}
UserList(group) {
$.getJSON('https://randomuser.me/api/' + group)
.then(({ results }) => this.setState({ person: results }));
}
render() {
return (...)
}
}
Update
componentWillReceiveProps() will be deprecated.
Here are only some methods (all of them in Doc) in the life cycle I think that they are related to deploying API in the general cases:
By referring to the diagram above:
Deploy API in componentDidMount()
The proper scenario to have API call here is that the content (from the response of API) of this component will be static, componentDidMount() only fire once while the component is mounting, even new props are passed from the parent component or have actions to lead re-rendering.
The component do check difference to re-render but not re-mount.
Quote from doc:
If you need to load data from a remote endpoint, this is a good place to
instantiate the network request.
Deploy API in static getDerivedStateFromProps(nextProps, prevState)
We should notice that there are two kinds of component updating, setState() in current component would not trigger this method but re-rendering or new props from parent component would.
We could find out this method also fires while mounting.
This is a proper place to deploy API if we want to use the current component as a template, and the new parameters to make API calls are props coming from parent component.
We receive a different response from API and return a new state here to change the content of this component.
For example:
We have a dropdown list for different Cars in the parent component, this component needs to show the details of the selected one.
Deploy API in componentDidUpdate(prevProps, prevState)
Different from static getDerivedStateFromProps(), this method is invoked immediately after every rendering except the initial rendering. We could have API calling and render difference in one component.
Extend the previous example:
The component to show Car's details may contain a list of series of this car, if we want to check the 2013 production one, we may click or select or ... the list item to lead a first setState() to reflect this behavior (such as highlighting the list item) in this component, and in the following componentDidUpdate() we send our request with new parameters (state). After getting the response, we setState() again for rendering the different content of the Car details. To prevent the following componentDidUpdate() from causing the infinity loop, we need to compare the state by utilizing prevState at the beginning of this method to decide if we send the API and render the new content.
This method really could be utilized just like static getDerivedStateFromProps() with props, but need to handle the changes of props by utilizing prevProps. And we need to cooperate with componentDidMount() to handle the initial API call.
Quote from doc:
... This is also a good place to do network requests as long as you
compare the current props to previous props ...
I would like you to have a look at redux
http://redux.js.org/index.html
They have very well defined way of handling async calls ie API calls, and instead of using jQuery for API calls, I would like to recommend using fetch or request npm packages, fetch is currently supported by modern browsers, but a shim is also available for server side.
There is also this another amazing package superagent, which has alot many options when making an API request and its very easy to use.
You can also fetch data with hooks in your function components
full example with api call: https://codesandbox.io/s/jvvkoo8pq3
second example: https://jsfiddle.net/bradcypert/jhrt40yv/6/
const Repos = ({user}) => {
const [repos, setRepos] = React.useState([]);
React.useEffect(() => {
const fetchData = async () => {
const response = await axios.get(`https://api.github.com/users/${user}/repos`);
setRepos(response.data);
}
fetchData();
}, []);
return (
<div>
{repos.map(repo =>
<div key={repo.id}>{repo.name}</div>
)}
</div>
);
}
ReactDOM.render(<Repos user="bradcypert" />, document.querySelector("#app"))
1) You can use Fetch API to fetch data from Endd Points:
Example fetching all Github repose for a user
/* Fetch GitHub Repos */
fetchData = () => {
//show progress bar
this.setState({ isLoading: true });
//fetch repos
fetch(`https://api.github.com/users/hiteshsahu/repos`)
.then(response => response.json())
.then(data => {
if (Array.isArray(data)) {
console.log(JSON.stringify(data));
this.setState({ repos: data ,
isLoading: false});
} else {
this.setState({ repos: [],
isLoading: false
});
}
});
};
2) Other Alternative is Axios
Using axios you can cut out the middle step of passing the results of
the http request to the .json() method. Axios just returns the data
object you would expect.
import axios from "axios";
/* Fetch GitHub Repos */
fetchDataWithAxios = () => {
//show progress bar
this.setState({ isLoading: true });
// fetch repos with axios
axios
.get(`https://api.github.com/users/hiteshsahu/repos`)
.then(result => {
console.log(result);
this.setState({
repos: result.data,
isLoading: false
});
})
.catch(error =>
this.setState({
error,
isLoading: false
})
);
}
Now you can choose to fetch data using any of this strategies in componentDidMount
class App extends React.Component {
state = {
repos: [],
isLoading: false
};
componentDidMount() {
this.fetchData ();
}
Meanwhile you can show progress bar while data is loading
{this.state.isLoading && <LinearProgress />}
Render function should be pure, it's mean that it only uses state and props to render, never try to modify the state in render, this usually causes ugly bugs and decreases performance significantly. It's also a good point if you separate data-fetching and render concerns in your React App. I recommend you read this article which explains this idea very well. https://medium.com/#learnreact/container-components-c0e67432e005#.sfydn87nm
This part from React v16 documentation will answer your question, read on about componentDidMount():
componentDidMount()
componentDidMount() is invoked immediately after a component is
mounted. Initialization that requires DOM nodes should go here. If you
need to load data from a remote endpoint, this is a good place to
instantiate the network request. This method is a good place to set up
any subscriptions. If you do that, don’t forget to unsubscribe in
componentWillUnmount().
As you see, componentDidMount is considered the best place and cycle to do the api call, also access the node, means by this time it's safe to do the call, update the view or whatever you could do when document is ready, if you are using jQuery, it should somehow remind you document.ready() function, where you could make sure everything is ready for whatever you want to do in your code...
As an addition/update to Oleksandr T.'s excellent answer:
If you use class components, backend calls should happen in componentDidMount.
If you use hooks instead, you should use the effect hook
For example:
import React, { useState, useEffect } from 'react';
useEffect(() => {
fetchDataFromBackend();
}, []);
// define fetchDataFromBackend() as usual, using Fetch API or similar;
// the result will typically be stored as component state
Further reading:
Using the Effect Hook in the official docs.
How to fetch data with React Hooks? by Robin Wieruch
A clean way is to make an asynchronous API call inside componentDidMount with try/catch function.
When we called an API, we receive a response. Then we apply JSON method on it, to convert the response into a JavaScript object. Then we take from that response object only his child object named "results" (data.results).
In the beginning we defined "userList" in state as an empty array. As soon as we make the API call and receive data from that API, we assign the "results" to userList using setState method.
Inside the render function we tell that userList will be coming from state. Since the userList is an array of objects we map through it, to display a picture, a name and a phone number of each object "user". To retrieve this information we use dot notation (e.g. user.phone).
NOTE: depending on your API, your response may look different. Console.log the whole "response" to see which variables you need from it, and then assign them in setState.
UserList.js
import React, { Component } from "react";
export default class UserList extends Component {
state = {
userList: [], // list is empty in the beginning
error: false
};
componentDidMount() {
this.getUserList(); // function call
}
getUserList = async () => {
try { //try to get data
const response = await fetch("https://randomuser.me/api/");
if (response.ok) { // ckeck if status code is 200
const data = await response.json();
this.setState({ userList: data.results});
} else { this.setState({ error: true }) }
} catch (e) { //code will jump here if there is a network problem
this.setState({ error: true });
}
};
render() {
const { userList, error } = this.state
return (
<div>
{userList.length > 0 && userList.map(user => (
<div key={user}>
<img src={user.picture.medium} alt="user"/>
<div>
<div>{user.name.first}{user.name.last}</div>
<div>{user.phone}</div>
<div>{user.email}</div>
</div>
</div>
))}
{error && <div>Sorry, can not display the data</div>}
</div>
)
}}
As best place and practice for external API calls is React Lifecycle method componentDidMount(), where after the execution of the API call you should update the local state to be triggered new render() method call, then the changes in the updated local state will be applied on the component view.
As other option for initial external data source call in React is pointed the constructor() method of the class. The constructor is the first method executed on initialization of the component object instance. You could see this approach in the documentation examples for Higher-Order Components.
The method componentWillMount() and UNSAFE_componentWillMount() should not be used for external API calls, because they are intended to be deprecated. Here you could see common reasons, why this method will be deprecated.
Anyway you must never use render() method or method directly called from render() as a point for external API call. If you do this your application will be blocked.
You must try "axios" library for API call.
Instead of direct using jQuery.
Thanks.
It would be great to use axios for the api request which supports cancellation, interceptors etc. Along with axios, l use react-redux for state management and redux-saga/redux-thunk for the side effects.
I have the App.js, inside of it a component. Name it Example. I want to set the Example's props with the App.states. For an example, Example has the props: name,id. In the App i want to fetch the data i want from the server, and set it as the App's states, then assign them to the Example's props, before the app renders it. The problem here is that i read about componentWillMount(), but the React documentation says that it's not the best way. Then, what's the best way?
General approach is to store ajax response inside App and when response has been saved into the state, render Example component with data fetched from response
class App extends React.Component
state = { response: null }
componentDidMount() {
runYouFetchHere
.then((response) => this.setState({ response }))
}
render() {
const { response } = this.state
if (response === null) { return null }
return (
<Example name={response.name} id={response.id} />
)
}
}
When there is an update in react component then any of the following update methods are called.
https://reactjs.org/docs/react-component.html#updating
Trying to set the state inside
componentWillRecieveProps(){
this.setState({ })
}
I think this question has been answer several time but I can't find my specific case.
https://codesandbox.io/s/jjy9l3003
So basically I have an App component that trigger an action that change a state call "isSmall" to true if the screen is resized and less than 500px (and false if it is higher)
class App extends React.Component {
...
resizeHandeler(e) {
const { window, dispatch } = this.props;
if (window.innerWidth < 500 && !this.state.isSmall) {
dispatch(isSmallAction(true));
this.setState({ isSmall: true });
} else if (window.innerWidth >= 500 && this.state.isSmall) {
dispatch(isSmallAction(false));
console.log(isSmallAction(false));
this.setState({ isSmall: false })
}
};
componentDidMount() {
const { window } = this.props;
window.addEventListener('resize', this.resizeHandeler.bind(this));
}
...
I have an other component called HeaderContainer who is a child of App and connected to the Store and the state "isSmall", I want this component to rerender when the "isSmall" change state... but it is not
class Header extends React.Component {
constructor(props) {
super(props);
this.isSmall = props.isSmall;
this.isHome = props.isHome;
}
...
render() {
return (
<div>
{
this.isSmall
?
(<div>Is small</div>)
:
(<div>is BIG</div>)
}
</div>
);
}
...
even if I can see through the console that redux is actually updating the store the Header component is not re-rendering.
Can someone point out what I am missing ?
Am I misunderstanding the "connect()" redux-react function ?
Looking at your code on the link you posted your component is connected to the redux store via connect
const mapStateToProps = (state, ownProps) => {
return {
isHome: ownProps.isHome,
isSmall: state.get('isSmall')
}
}
export const HeaderContainer = connect(mapStateToProps)(Header);
That means that the props you are accessing in your mapStateToProps function (isHome and isSmall) are taken from the redux store and passed as props into your components.
To have React re-render your component you have to use 'this.props' inside the render function (as render is called every time a prop change):
render() {
return (
<div>
{
this.props.isSmall
?
(<div>Is small</div>)
:
(<div>is BIG</div>)
}
</div>
);
}
You are doing it well in the constructor but the constructor is only called once before the component is mounted. You should have a look at react lifecycle methods: https://reactjs.org/docs/react-component.html#constructor
You could remove entirely the constructor in your Header.js file.
You should also avoid using public class properties (e.g. this.isSmall = props.isSmall; ) in react when possible and make use of the React local state when your component needs it: https://reactjs.org/docs/state-and-lifecycle.html#adding-local-state-to-a-class
A component is only mounted once and then only being updated by getting passed new props. You constructor is therefore only being called once before mount. That means that the instance properties you set there will never change during the lifetime of your mounted component. You have to directly Access this.props in your render() function to make updating work. You can remove the constructor as he doesn't do anything useful in this case.
Id like to create a view that stays up to date, by making new API calls every minute. Basically needing to trigger all child components to rerender, and make their API call again. Ive tried using forceUpdate(), as well as updating the prop (below). The timer is working, but the child components are not calling the API for more data
Currently the component looks like this:
class MyComponent extends React.Component<Props, State> {
state = {
time: 0
};
private interval : any;
componentDidMount() {
this.interval = setInterval(this._refreshPage.bind(this), 1000);
}
componentWillUnmount() {
clearInterval(this.interval);
}
_refreshPage() {
console.log("refresh");
//this.forceUpdate();
this.setState({ time: Date.now() });
}
render () {
return (
<div className="MyComponent">
<Api endpoint={'/api/revenue/total_revenue?' + this.state.time} loadData={true}>
<Table />
</Api>
...
Api:
class Api extends React.Component {
componentDidMount() {
this._makeApiCall(this.props.endpoint);
}
...
I was hoping here, that as the prop query parameter changed with the nuw timestamp (which it does), the Api component would rerender and call the "new" endpoint. The prop does change, however the API does not get called again, why?
Use a different lifecycle method. componentDidMount is only called the first time the component is added to the dom, not during any subsequent re-renders. shouldComponentUpdate is probably the one you want.
Here I'm trying to get value from DefaultOpts.jsx and update the values to setState in Filters.jsx. But I'm getting error as below :
setState(...): Cannot update during an existing state transition (such as within render or another component's constructor). Render methods should be a pure function of props and state; constructor side-effects are an anti-pattern, but can be moved to componentWillMount.
Filters.jsx
import React from 'react';
import DefaultOpts from 'DefaultOpts.jsx';
export default class Filters extends React.Component {
constructor(props) {
super(props);
this.state = {
vOptions : []
}
this.handleOptions = this.handleOptions.bind(this)
}
handleOptions(params) {
console.log(params)
this.setState({
vOptions : params
});
}
componentDidMount() {
}
componentDidUpdate() {
}
render() {
return (
<div>
<DefaultOpts handleOptions={this.handleOptions.bind(this)} />
</div>
)
}
}
DefaultOpts.jsx
import React from 'react';
class DefaultOpts extends React.Component{
constructor(props) {
super(props);
}
componentDidMount() {
}
componentDidUpdate() {
}
render() {
var optArray = "";
$.ajax({
type: "get",
url: "url-path",
success: function(data) {
optArray = data;
}
});
return (
<div>
{this.props.handleOptions(optArray)}
</div>
)
}
}
export default DefaultOpts;
I got some answers in stackoverflow but I'm not able to get what's issue in my code. Please suggest me here what's wrong in my code..
You can't call this.props.handleOptions inside the render because it will trigger setState of the parent component - and you are still inside the rendering process. That's why it complains.
Try to execute this function inside the componentDidMount (together with your ajax call)
There are several problems with your code:
1) First and main one that results in the mentioned error is the fact that by calling handleOptions in render you are calling setState that in turn starts react life cycle. This is a really bad practice and always should/can be avoided.
2) You have one more async call to $.ajax in render that does not directly result in updating state but still considered a bad practice.
To conclude - your render function must not result in any app logic being performed, its task is to render results that have already been prepared. Do all heavy/async work in componentDidMount/componentDidUpdate and you will be fine.
render will execute before didMount... so you are setting the state before it is mounted
anyway move the $.ajax call to didMount, you shouldn't be doing logic things in render()