Can Reactjs Programmatically Handle :Before

Can Reactjs programmatically handle :before?

Pseudo elements cannot be styled with inline styles as explained in https://stackoverflow.com/a/14141821/368697. You will have to style the something class name in a stylesheet with the .something:before selector. This is not a limitation of React but rather a design choice for HTML + CSS.

If you need to programmatically change the width of the pseudo :before element, it is probably more appropriate as a regular DOM element rendered by React.

Can Reactjs programmatically handle :before?

Pseudo elements cannot be styled with inline styles as explained in https://stackoverflow.com/a/14141821/368697. You will have to style the something class name in a stylesheet with the .something:before selector. This is not a limitation of React but rather a design choice for HTML + CSS.

If you need to programmatically change the width of the pseudo :before element, it is probably more appropriate as a regular DOM element rendered by React.

Programmatically navigate using React router

React Router v5.1.0 with hooks

There is a new useHistory hook in React Router >5.1.0 if you are using React >16.8.0 and functional components.

import { useHistory } from "react-router-dom";

function HomeButton() {
  const history = useHistory();

  function handleClick() {
    history.push("/home");
  }

  return (
    <button type="button" onClick={handleClick}>
      Go home
    </button>
  );
}

React Router v4

With v4 of React Router, there are three approaches that you can take to programmatic routing within components.

1. Use the withRouter higher-order component.
2. Use composition and render a <Route>
3. Use the context.

React Router is mostly a wrapper around the history library. history handles interaction with the browser's window.history for you with its browser and hash histories. It also provides a memory history which is useful for environments that don't have a global history. This is particularly useful in mobile app development (react-native) and unit testing with Node.

A history instance has two methods for navigating: push and replace. If you think of the history as an array of visited locations, push will add a new location to the array and replace will replace the current location in the array with the new one. Typically you will want to use the push method when you are navigating.

In earlier versions of React Router, you had to create your own history instance, but in v4 the <BrowserRouter>, <HashRouter>, and <MemoryRouter> components will create a browser, hash, and memory instances for you. React Router makes the properties and methods of the history instance associated with your router available through the context, under the router object.

1. Use the withRouter higher-order component

The withRouter higher-order component will inject the history object as a prop of the component. This allows you to access the push and replace methods without having to deal with the context.

import { withRouter } from 'react-router-dom'
// this also works with react-router-native

const Button = withRouter(({ history }) => (
  <button
    type='button'
    onClick={() => { history.push('/new-location') }}
  >
    Click Me!
  </button>
))

2. Use composition and render a <Route>

The <Route> component isn't just for matching locations. You can render a pathless route and it will always match the current location. The <Route> component passes the same props as withRouter, so you will be able to access the history methods through the history prop.

import { Route } from 'react-router-dom'

const Button = () => (
  <Route render={({ history}) => (
    <button
      type='button'
      onClick={() => { history.push('/new-location') }}
    >
      Click Me!
    </button>
  )} />
)

3. Use the context*

But you probably should not

The last option is one that you should only use if you feel comfortable working with React's context model (React's Context API is stable as of v16).

const Button = (props, context) => (
  <button
    type='button'
    onClick={() => {
      // context.history.push === history.push
      context.history.push('/new-location')
    }}
  >
    Click Me!
  </button>
)

// you need to specify the context type so that it
// is available within the component
Button.contextTypes = {
  history: React.PropTypes.shape({
    push: React.PropTypes.func.isRequired
  })
}

1 and 2 are the simplest choices to implement, so for most use cases, they are your best bets.

How to manually trigger click event in ReactJS?

You could use the ref prop to acquire a reference to the underlying HTMLInputElement object through a callback, store the reference as a class property, then use that reference to later trigger a click from your event handlers using the HTMLElement.click method.

In your render method:

<input ref={input => this.inputElement = input} ... />

In your event handler:

this.inputElement.click();

Full example:

class MyComponent extends React.Component {
  render() {
    return (
      <div onClick={this.handleClick}>
        <input ref={input => this.inputElement = input} />
      </div>
    );
  }

  handleClick = (e) => {
    this.inputElement.click();
  }
}

Note the ES6 arrow function that provides the correct lexical scope for this in the callback. Also note, that the object you acquire this way is an object akin to what you would acquire using document.getElementById, i.e. the actual DOM-node.

Programmatically routing after login in React

In general, you should lift the state up so that you'll trigger a re-render in the right place. In this example, you can see the difference between triggering the state in different places.

import React, { Component } from 'react';
import { render } from 'react-dom';

class Child extends React.Component {
  state = {
    loggedIn: false,
  }

  toggle = () => {
    this.setState({ loggedIn: !this.state.loggedIn })
  }

  render() {
    return <p onClick={this.props.onClick || this.toggle}>I am {this.state.loggedIn ? 'in' : 'out'}</p>
  }
}

class App extends Component {
  state = {
    loggedIn: false,
  }

  toggle = () => {
    this.setState({ loggedIn: !this.state.loggedIn })
  }

  render() {
    return (
      <React.Fragment>
        <Child onClick={this.toggle} />
        <Child />
      </React.Fragment>
    );
  }
}

render(<App />, document.getElementById('root'));

Here is a live example.

What is the best way to trigger onchange event in react js

For React 16 and React >=15.6

Setter .value= is not working as we wanted because React library overrides input value setter but we can call the function directly on the input as context.

var nativeInputValueSetter = Object.getOwnPropertyDescriptor(window.HTMLInputElement.prototype, "value").set;
nativeInputValueSetter.call(input, 'react 16 value');

var ev2 = new Event('input', { bubbles: true});
input.dispatchEvent(ev2);

For textarea element you should use prototype of HTMLTextAreaElement class.

New codepen example.

All credits to this contributor and his solution

Outdated answer only for React <=15.5

With react-dom ^15.6.0 you can use simulated flag on the event object for the event to pass through

var ev = new Event('input', { bubbles: true});
ev.simulated = true;
element.value = 'Something new';
element.dispatchEvent(ev);

I made a codepen with an example

To understand why new flag is needed I found this comment very helpful:

The input logic in React now dedupe's change events so they don't fire
more than once per value. It listens for both browser onChange/onInput
events as well as sets on the DOM node value prop (when you update the
value via javascript). This has the side effect of meaning that if you
update the input's value manually input.value = 'foo' then dispatch a
ChangeEvent with { target: input } React will register both the set
and the event, see it's value is still `'foo', consider it a duplicate
event and swallow it.

This works fine in normal cases because a "real" browser initiated
event doesn't trigger sets on the element.value. You can bail out of
this logic secretly by tagging the event you trigger with a simulated
flag and react will always fire the event.
https://github.com/jquense/react/blob/9a93af4411a8e880bbc05392ccf2b195c97502d1/src/renderers/dom/client/eventPlugins/ChangeEventPlugin.js#L128

how react programmatically focus input

The way you have used refs is not the most preferred way or else its not the best practice anymore . try some thing like this

class MyClass extends React.Component {
  constructor(props) {
    super(props);
    this.focus = this.focus.bind(this);
  }

  focus() {
    this.textInput.current.focus();
  }

  render() {

    return (
      <div>
        <input
          type="text"
          ref={(input) => { this.textInput = input; }} />
        <input
          type="button"
          value="Set Focus"
          onClick={this.focus}
        />
      </div>
    );
  }
}

Update
From React 16.3 upwards you can use the React.createRef() API

class MyClass extends React.Component {
  constructor(props) {
    super(props);
    // create a ref to store the textInput DOM element
    this.textInput = React.createRef();
    this.focus = this.focus.bind(this);
  }

  focus() {
    // Explicitly focus the text input using the raw DOM API
    // Note: we're accessing "current" to get the DOM node
    this.textInput.current.focus();
  }

  render() {
    // tell React that we want to associate the <input> ref
    // with the `textInput` that we created in the constructor
    return (
      <div>
        <input
          type="text"
          ref={this.textInput} />
        <input
          type="button"
          value="Set Focus"
          onClick={this.focus}
        />
      </div>
    );
  }
}

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