I need to test a react components with props mounts ok and renders its content such as paras and divs correctly. My code can be found below or in this sandbox
I tried testing it with a default prop but that didn't work.
import React from 'react';
import test from 'tape';
import {mount} from 'enzyme';
test('testing', t => {
t.doesNotThrow(() => {
wrapper = mount(<App2 txt={ok}/>);
}, 'Should mount');
t.end();
});
And this is my component with props.
import React, { Component } from 'react';
import { render } from 'react-dom';
import Hello from './Hello';
import './style.css';
import App from './index'
export default class App2 extends Component {
constructor() {
super();
this.state = {
name: 'React'
};
}
render() {
const {txt}=this.props
return (
<div>
<p>hi {txt}</p>
</div>
);
}
}
And the outer component supplying the prop.
import React, { Component } from 'react';
import { render } from 'react-dom';
import Hello from './Hello';
import './style.css';
import App2 from './app2'
class App extends Component {
constructor() {
super();
this.state = {
name: 'React'
};
}
render() {
return (
<div>
<Hello name={this.state.name} />
<p>
Start editing to see some magic happen :)
</p>
<App2 txt={this.state.name}/>
</div>
);
}
}
render(<App />, document.getElementById('root'));
So you would do something like providing the properties yourself and ensuring that it renders with them:
test('test your component', () => {
const wrapper = mount(<App2 txt={'michaelangelo'} />);
expect(wrapper.find('p').text()).toEqual('hi michaelangelo');
});
You shouldn't worry about testing the and html elements like that, but rather the props that you pass and that they render in the right place i.e., in the p tag
Related
I have to implement hooks in my Component, but as far as I know it is not possible using the hooks in a REACT.Component.. I am new at REACT and I don´t really have an Idea how I can convert my Component to a function correctly. Can someone show me how to convert the content from my Component to this function?
My Component:
import React from "react";
import { sessionId } from "../common/urlHandler";
import { Settings } from "../settings";
import { Constants } from "../common/constants.js";
import OrderHistoryService from "../services/orderHistory/orderHistoryService";
import OrderHistoryTable from "../orderHistory/orderHistoryTable";
import OrderHistoryPagination from "../orderHistory/orderHistoryPagination";
import OrderHistorySearchField from "../orderHistory/orderHistorySearchField";
export default class OrderHistoryPage extends React.Component {
constructor(props) {
super(props);
const orderHistoryService = new OrderHistoryService(
Settings.baseUrl,
this.props.lang
);
this.state = {
orderHistoryService: orderHistoryService,
sessionId: sessionId(),
orderHistoryData: Constants.DummyOrderHistory,
};
}
componentDidMount() {
//fixMe: fetch-Data and set orderHistoryData
}
render() {
if (this.state.orderHistoryData !== null) {
return (
<section className="section">
<div><OrderHistorySearchField /></div>
<div><OrderHistoryPagination /></div>
<div><OrderHistoryTable orderHistoryData={this.state.orderHistoryData} /></div>
</section>
);
}
}
}
The function into I want to convert my Component:
export default function OrderHistoryPage () {
//fill with data from my Component
}
It should be like this basically you should use useState for states and useEffect for componentDidMount. Also you should remove things that does not exist in functional components like render and this.
import React, {useState, useEffect} from "react";
import { sessionId } from "../common/urlHandler";
import { Settings } from "../settings";
import { Constants } from "../common/constants.js";
import OrderHistoryService from "../services/orderHistory/orderHistoryService";
import OrderHistoryTable from "../orderHistory/orderHistoryTable";
import OrderHistoryPagination from "../orderHistory/orderHistoryPagination";
import OrderHistorySearchField from "../orderHistory/orderHistorySearchField";
export default function OrderHistoryPage (props) {
const orderHistoryService = new OrderHistoryService(
Settings.baseUrl,
props.lang
);
const [orderHistoryService, setorderHistoryService] = useState(orderHistoryService);
const [sessionId, setSessionId] = useState(sessionId());
const [orderHistoryData, setOrderHistoryData] = useState(Constants.DummyOrderHistory);
useEffect(()=> {
//fixMe: fetch-Data and set orderHistoryData
}, []);
return (
{ (orderHistoryData !== null) &&
(<section className="section">
<div><OrderHistorySearchField /></div>
<div><OrderHistoryPagination /></div>
<div><OrderHistoryTable orderHistoryData={this.state.orderHistoryData} /></div>
</section>) }
);
}
I have a function ChartWrapper and a class called LineChart.
All the code:
index.js ->
import React from 'react';
import ReactDOM from 'react-dom';
import './index.css';
import App from './App';
import * as serviceWorker from './serviceWorker';
ReactDOM.render(
<React.StrictMode>
<App />
</React.StrictMode>,
document.getElementById('root')
);
serviceWorker.unregister();
App.js ->
import React, {useRef, useEffect, useState, Component} from 'react';
import './App.css';
import ChartWrapper from './ChartWrapper'
class App extends Component {
render() {
return (
<div id="app">
<ChartWrapper />
</div>
)
}
}
export default App;
ChartWrapper.js ->
import React, {Component, useEffect} from 'react';
import { useRef } from 'react';
import LineChart from './LineChart'
function ChartWrapper() {
const svgRef = useRef();
console.log("works");
useEffect( () => {
const chart = <LineChart parent = {svgRef} />
console.log(chart);
}, []);
return (
<svg ref={svgRef}>
</svg>
);
}
export default ChartWrapper;
LineChart.js ->
import React, {Component} from 'react'
import {scaleLinear} from 'd3-scale'
import {max} from 'd3-array'
import {select} from 'd3-selection'
class LineChart extends Component {
constructor (props) {
super(props);
this.svg = select(props.parent);
console.log("does this work");
console.log(this.svg);
}
}
export default LineChart;
The ChartWrapper function creates a LineChart object and passes a const as a prop. To check if the code is working, I have print statements. For some reason, the print statements in ChartWrapper work fine. The print statements in LineChart constructor class however do not.
Am I missing something?
What you get in return when you log chart to the console is just an object representing the component, like this:
If you look at the type, it specifies the function/class to call. The class is only instantiated when it's rendered.
And the chart component is not returned, therefore react does not render it.
you need to call the render method for LineChart
I am trying to pass a value from a context provider to a consumer using useContext and access the value outside of the render function.
My provider looks like so:
export const AppContext = React.createContext();
export class App extends React.Component(){
render(){
<AppContext.Provider value={{ name: 'John' }} ><Main /></AppContext>
}
}
My consumer looks like so
import React, { useContext } from 'react';
import { AppContext } from './App';
export class Main extends React.Component(){
componentDidMount(){
const value = useContext(AppContext);
}
render(){
return (
<div>Main Component</div>
)
}
}
The error is this:
Invalid hook call. Hooks can only be called inside of the body of a function component.
If you want to use hooks they are designed for function components. Like so:
import React, { useContext } from 'react';
import { AppContext } from './App';
const Main = () => {
const value = useContext(AppContext);
return(
<div>Main Component</div>
);
}
If you want to use it in a class based component then just set it as a static contextType in your class and then you can use it with this.context in your component like so:
import React from 'react';
import { AppContext } from './App';
class Main extends React.Component(){
static contextType = AppContext;
componentDidMount(){
const value = this.context;
}
render(){
return (
<div>Main Component</div>
)
}
}
Edit:
Remove your context from your app component and place it in its own component. I think you are receiving conflicts in your exporting of your context.
so your app component should look like:
import React from "react";
import Context from "./Context";
import Main from "./Main";
class App extends React.Component {
render() {
return (
<Context>
<Main />
</Context>
);
}
}
export default App;
Your main component should be like:
import React from "react";
import { AppContext } from "./Context";
class Main extends React.Component {
static contextType = AppContext;
render() {
return <div>{this.context.name}</div>;
}
}
export default Main;
and your context component should be like:
import React from "react";
export const AppContext = React.createContext();
class Context extends React.Component {
state = {
name: "John"
};
//Now you can place all of your logic here
//instead of cluttering your app component
//using this components state as your context value
//allows you to easily write funcitons to change
//your context just using the native setState
//you can also place functions in your context value
//to call from anywhere in your app
render() {
return (
<AppContext.Provider value={this.state}>
{this.props.children}
</AppContext.Provider>
);
}
}
export default Context;
Here is a sandbox to show you it working CodSandbox
You get the above error because Hooks are meant to be used inside functional components and not class component whereas you try to use it within componentDidMount of Main component which is a class component
You can rewrite your code for Main component using useContext hook like
import React, { useContext } from 'react';
import { AppContext } from './App';
export const Main =() =>{
const value = useContext(AppContext);
return (
<div>Main Component</div>
)
}
or use Context in a different way with class like
import React from 'react';
import { AppContext } from './App';
class Main extends React.Component {
componentDidMount(){
const value = this.context;
// use value here. Also if you want to use context elsewhere in class
// you can use if from this.context
}
render(){
return (
<div>Main Component</div>
)
}
}
Main.contextType = AppContext;
export { Main };
Hooks only work with stateless components. You are trying to use it in class component.
Here is the content for Main.js file. Uncomment the commented part if you want to use class-based component instead of the functional one.
import React from "react";
import { AppContext } from "./App";
/** UNCOMMENT TO USE REACT CLASS COMPONENT */
// class Main extends React.Component() {
// render() {
// return (
// <AppContext.Consumer>
// {value => <div>It's Main component. Context value is ${value.name}</div>}
// </AppContext.Consumer>
// );
// }
// }
const Main = () => {
const value = React.useContext(AppContext);
return <div>It's Main component. Context value is ${value.name}</div>;
};
export default Main;
Here is the content for App.js file. Uncomment the commented part if you want to use class-based component instead of the functional one.
import React from "react";
import ReactDOM from "react-dom";
import Main from "./Main";
export const AppContext = React.createContext();
/** UNCOMMENT TO USE REACT CLASS COMPONENT */
// export class App extends React.Component() {
// render() {
// return (
// <AppContext.Provider value={{ name: "John" }}>
// <Main />
// </AppContext.Provider>
// );
// }
// }
const App = () => (
<AppContext.Provider value={{ name: "John" }}>
<Main />
</AppContext.Provider>
);
const rootElement = document.getElementById("root");
ReactDOM.render(<App />, rootElement);
React Hooks were implemented directly for the functional components in order to give them the possibility to become stateful. Class-based components were stateful all the time, so you have to use their own state API.
Working demo is available here.
I want to pass a value to a div with id good in my index.html but it brings this error, Objects are not valid as a React child (found: [object HTMLDivElement]). If you meant to render a collection of children, use an array instead. in TestComponent (at App.js:49)
in div (at App.js:28)
in Apps (at index.js:7)
Please what am I doing wrong
TestComponent.js
import React, { Component } from 'react';
class TestComponent extends Component {
componentDidMount(){
console.log("Great");
}
render() {
// var {test} = this.props;
return (
<p>
{this.props.test}
</p>,
document.getElementById("good")
);
}
}
export default TestComponent;
App.js
import React, { Component } from 'react';
import ReactDOM from 'react-dom';
import './index.css';
import TestComponent from "./components/TestComponent"
class Apps extends Component {
constructor(props){
super(props);
}
render() {
return (
<div>
<TestComponent test='doyin'/>
</div>
);
}
}
export default Apps;
Index.html
<div id="good"></div>
A class Component render function shouldn't use document.getElementById, you need to use ReactDOM.render to do that
import React, { Component } from 'react';
class TestComponent extends Component {
componentDidMount(){
console.log("Great");
}
render() {
// var {test} = this.props;
return (
<p>
{this.props.test}
</p>
);
}
}
export default TestComponent;
App
class Apps extends Component {
constructor(props){
super(props);
}
render() {
return (
<div>
<TestComponent test='doyin'/>
</div>
);
}
}
ReactDOM.render(<Apps />, document.getElementById("good"))
export default Apps;
In TestComponent.js, inside render function you are trying to return two elements, <p> and document.getElementById("good"). Probably you just wanted to return <p>:
render() {
return <p>{this.props.test}</p>;
}
Also, it looks like you've mistaken React.Component.render with ReactDOM.render(element, container[, callback]) where the second argument of the functions is the container.
So the full error is as follows...
Warning: React.createElement: type should not be null, undefined,
boolean, or number. It should be a string (for DOM elements) or a ReactClass (for
composite components). Check the render method of `IndexBody.
I'm not sure why I'm receiving this error, I thought I created my component properly but maybe another eye can see what I'm doing wrong.
index.jsx:
import React, { PropTypes } from 'react';
import ReactDOM from 'react-dom';
import Test from './app';
class IndexBody extends React.Component {
render() {
return (
<div>
<h1>This will show the Test Component</h1>
<Test />
</div>
);
}
}
ReactDOM.render(<IndexBody />, document.getElementById('react-app'))
And my imported Test component from ./app.jsx
import React, { PropTypes } from 'react';
import ReactDOM from 'react-dom';
class Test extends React.Component {
constructor(props) {
super(props);
this.state = {
hello: 'hello world',
};
}
render() {
console.log('WORKS'); // logs fine
return (
<div>
<h1>{this.state.hello}</h1>
</div>
);
}
}
ReactDOM.render(<Test/>, document.getElementById('react-app'));
I'm able to display the log, but it doesn't want to render the component. Am I incorrectly creating components? Thank you for your help in advance!
You don't export Test from app.jsx.
This means it's not available as an import, thus the undefined.
Based on your current code you'd need to add:
export default Test;
to app.jsx.
Dave is correct, you need to do export default Test; at the bottom of App.jsx. Also, you only want one ReactDOM.render() function in you entire app, index.jsx loads the component tree it all gets passed to ReactDOM.render() in the one file (index.jsx).
So in your case just change app.jsx to this and you should be in business:
import React, { PropTypes } from 'react';
import ReactDOM from 'react-dom';
class Test extends React.Component {
constructor(props) {
super(props);
this.state = {
hello: 'hello world',
};
}
render() {
console.log('WORKS'); // logs fine
return (
<div>
<h1>{this.state.hello}</h1>
</div>
);
}
}
export default Test;