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React JS onClick event handler

Posted by: admin November 30, 2017 Leave a comment

Questions:

I have

var TestApp = React.createClass({
      getComponent: function(){
          console.log(this.props);
      },
      render: function(){
        return(
             <div>
             <ul>
                <li onClick={this.getComponent}>Component 1</li>
             </ul>
             </div>
        );
      }
});
React.renderComponent(<TestApp />, document.body);

I want to color the background of the clicked list element. How can I do this in React ?

Something like

$('li').on('click', function(){
    $(this).css({'background-color': '#ccc'});
});
Answers:

Two ways I can think of are

var TestApp = React.createClass({
    getComponent: function(index) {
        $(this.getDOMNode()).find('li:nth-child(' + index + ')').css({
            'background-color': '#ccc'
        });
    },
    render: function() {
        return (
            <div>
              <ul>
                <li onClick={this.getComponent.bind(this, 1)}>Component 1</li>
                <li onClick={this.getComponent.bind(this, 2)}>Component 2</li>
                <li onClick={this.getComponent.bind(this, 3)}>Component 3</li>
              </ul>
            </div>
        );
    }
});
React.renderComponent(<TestApp /> , document.getElementById('soln1'));

This is my personal favorite.

var ListItem = React.createClass({
    getInitialState: function() {
        return {
            isSelected: false
        };
    },
    handleClick: function() {
        this.setState({
            isSelected: true
        })
    },
    render: function() {
        var isSelected = this.state.isSelected;
        var style = {
            'background-color': ''
        };
        if (isSelected) {
            style = {
                'background-color': '#ccc'
            };
        }
        return (
            <li onClick={this.handleClick} style={style}>{this.props.content}</li>
        );
    }
});

var TestApp2 = React.createClass({
    getComponent: function(index) {
        $(this.getDOMNode()).find('li:nth-child(' + index + ')').css({
            'background-color': '#ccc'
        });
    },
    render: function() {
        return (
            <div>
             <ul>
              <ListItem content="Component 1" />
              <ListItem content="Component 2" />
              <ListItem content="Component 3" />
             </ul>
            </div>
        );
    }
});
React.renderComponent(<TestApp2 /> , document.getElementById('soln2'));

Here is a DEMO

I hope this helps.

Questions:
Answers:

Why not just:

onItemClick: function (event) {

    event.currentTarget.style.backgroundColor = '#ccc';

},

render: function() {
    return (
        <div>
            <ul>
                <li onClick={this.onItemClick}>Component 1</li>
            </ul>
        </div>
    );
}

And if you want to be more React-ive about it, you might want to set the selected item as state of its containing React component, then reference that state to determine the item’s color within render:

onItemClick: function (event) {

    this.setState({ selectedItem: event.currentTarget.dataset.id });
    //where 'id' =  whatever suffix you give the data-* li attribute
},

render: function() {
    return (
        <div>
            <ul>
                <li onClick={this.onItemClick} data-id="1" className={this.state.selectedItem == 1 ? "on" : "off"}>Component 1</li>
                <li onClick={this.onItemClick} data-id="2" className={this.state.selectedItem == 2 ? "on" : "off"}>Component 2</li>
                <li onClick={this.onItemClick} data-id="3" className={this.state.selectedItem == 3 ? "on" : "off"}>Component 3</li>
            </ul>
        </div>
    );
},

Of course, you’d want to put those <li>s into a loop, and you need to make the li.on and li.off styles set your background-color.

Questions:
Answers:

Here is how you define a react onClick event handler, which was answering the question title… using es6 syntax

import React, { Component } from 'react';

export default class Test extends Component {
  handleClick(event) {
    event.preventDefault()
    var el = event.target
    console.log(el)
  }

  render() {
    return (
      <a href='#' onClick={this.handleClick.bind(this)}>click me</a>
    )
  }
}

Questions:
Answers:

Use ECMA2015. Arrow functions make “this” a lot more intuitive.

import React from 'react';


class TestApp extends React.Component {
   getComponent(e, index) {
       $(e.target).css({
           'background-color': '#ccc'
       });
   }
   render() {
       return (
           <div>
             <ul>
               <li onClick={(e) => this.getComponent(e, 1)}>Component 1</li>
               <li onClick={(e) => this.getComponent(e, 2)}>Component 2</li>
               <li onClick={(e) => this.getComponent(e, 3)}>Component 3</li>
             </ul>
           </div>
       );
   }
});
React.renderComponent(<TestApp /> , document.getElementById('soln1'));`

Questions:
Answers:

If you’re using ES6, here’s some simple example code:

import React from 'wherever_react_is';

class TestApp extends React.Component {

  getComponent(event) {
      console.log('li item clicked!');
      event.currentTarget.style.backgroundColor = '#ccc';
  }

  render() {
    return(
       <div>
         <ul>
            <li onClick={this.getComponent.bind(this)}>Component 1</li>
         </ul>
       </div>
    );
  }
}

export default TestApp;

In ES6 class bodies, functions no longer require the ‘function’ keyword and they don’t need to be separated by commas. You can also use the => syntax as well if you wish.

Here’s an example with dynamically created elements:

import React from 'wherever_react_is';

class TestApp extends React.Component {

constructor(props) {
  super(props);

  this.state = {
    data: [
      {name: 'Name 1', id: 123},
      {name: 'Name 2', id: 456}
    ]
  }
}

  getComponent(event) {
      console.log('li item clicked!');
      event.currentTarget.style.backgroundColor = '#ccc';
  }

  render() {        
       <div>
         <ul>
         {this.state.data.map(d => {
           return(
              <li key={d.id} onClick={this.getComponent.bind(this)}>{d.name}</li>
           )}
         )}
         </ul>
       </div>
    );
  }
}

export default TestApp;

Note that each dynamically created element should have a unique reference ‘key’.

Furthermore, if you would like to pass the actual data object (rather than the event) into your onClick function, you will need to pass that into your bind. For example:

New onClick function:

getComponent(object) {
    console.log(object.name);
}

Passing in the data object:

{this.state.data.map(d => {
    return(
      <li key={d.id} onClick={this.getComponent.bind(this, d)}>{d.name}</li>
    )}
)}

Questions:
Answers:

Handling events with React elements is very similar to handling events
on DOM elements. There are some syntactic differences:

  • React events are named using camelCase, rather than lowercase.
  • With JSX you pass a function as the event handler, rather than a string.

So as mentioned in React documentation, they quite similar to normal HTML when it comes to Event Handling, but event names in React using camelcase, because they are not really HTML, they are JavaScript, also, you pass the function while we passing function call in a string format for HTML, they are different, but the concepts are pretty similar…

Look at the example below, pay attention to the way event get passed to the function:

function ActionLink() {
  function handleClick(e) {
    e.preventDefault();
    console.log('The link was clicked.');
  }

  return (
    <a href="#" onClick={handleClick}>
      Click me
    </a>
  );
}

Questions:
Answers:

Better Way to use onclick event :- Pass Paramter also

moreService(serviceList,e){
    this.setState({serviceList:serviceList,parentid:serviceList.sid})
    var updatebreadcrumb  =   this.props.updatebreadcrumb;
    updatebreadcrumb(serviceList);

 }


onClick={(e)=>this.moreService(value,e)}

Questions:
Answers:

Please comment if you downvote. This is a non-standard (but not so uncommon) React pattern that doesn’t use JSX, instead putting everything inline. Also, it’s Coffeescript.

The ‘React-way’ to do this would be with the component’s own state:

(c = console.log.bind console)

mock_items: [
    {
        name: 'item_a'
        uid: shortid()
    }
    {
        name: 'item_b'
        uid: shortid()
    }
    {
        name: 'item_c'
        uid: shortid()
    }
]
getInitialState: ->
    lighted_item: null
render: ->
    div null,
        ul null,
            for item, idx in @mock_items
                uid = item.uid
                li
                    key: uid
                    onClick: do (idx, uid) =>
                        (e) =>
                            # justf to illustrate these are bound in closure by the do lambda,
                            c idx
                            c uid
                            @setState
                                lighted_item: uid
                    style:
                        cursor: 'pointer'
                        background: do (uid) =>
                            c @state.lighted_item
                            c 'and uid', uid
                            if @state.lighted_item is uid then 'magenta' else 'chartreuse'
                        # background: 'chartreuse'
                    item.name

This example works — I tested it locally.
You can check out this example code exactly at my github.
Originally the env was only local for my own whiteboard r&d purposes but I posted it to Github for this. It may get written over at some point but you can check out the commit from Sept 8, 2016 to see this.

More generally, if you want to see how this CS/no-JSX pattern for React works, check out some recent work here. It’s possible I will have time to fully implement a POC for this app idea, the stack for which includes NodeJS, Primus, Redis, & React.