scope of "this" in module.exports

Question

I am turning a React.js component into a Common.js module using module.exports and am having an issue accessing "this" in the context of the component element from one of it's methods.

Below is the entire component. I have placed a comment above the line where the problem occurs. I did try a less verbose example at first but I do not think it was sufficient to explain the issue.

    var React = require('react');
    var GSAP  = require('gsap');

    var Psychedelicon = React.createClass({  

        cycleColors: function() {
            var touchPlatforms = ['iPhone', 'iPad', 'iPod', 'Android', 'Linux armv7l', 'WinCE'];
                       isTouch  = false;
                       iDevice  = false;
                       isDroid  = false;
                       plat = navigator.platform;

            if(plat === 'iPhone' || plat === 'iPad' || plat === 'iPod') {
                isTouch  = true;
                iDevice  = true;
            }
            else if (plat === 'Linux armv7l' || plat === 'Android') {
                isTouch  = true;
                isDroid  = true;
            }
            else {
                for (var i = 0; i < touchPlatforms.length; i++) {
                    if (plat === touchPlatforms[i]) {
                        isTouch = true;
                        break;
                    }
                    else {
                        isTouch = false;
                    }
                }
            }

            var isIE = false
                if (navigator.userAgent.toLowerCase().indexOf('msie') > -1 || navigator.userAgent.toLowerCase().indexOf('trident') > -1) {
                isIE = true
            }

            var isFF = false
                if (navigator.userAgent.toLowerCase().indexOf('firefox') != -1) {
                isFF = true
            }

            if(!isTouch) {
                var ColorSwirl = function(colorSet,defaultColor,time) {
                    var storedResult;
                    var randomColor = function(theArray) {
                        var result = theArray[Math.floor(Math.random() * (theArray.length))];
                        if(result === storedResult){
                            return(defaultColor)                        
                        }
                        else {
                            storedResult = result;
                            return(result);
                        }
                    }
                    var theLuckyColors = {top:randomColor(colorSet),bottom:randomColor(colorSet)};
                    var swirl = function(){
    //!!!!On this line the problem occurs onUpdateParams must reference the element accepting the execution event (onMouseEneter)
                        TweenLite.to(theLuckyColors, time, {colorProps:{top:randomColor(colorSet), bottom:randomColor(colorSet)}, onUpdate:colorize, onUpdateParams:[this],onComplete:swirl});
                    }
 gradients
                    var colorize = function(el) {
                        if(isIE) {
                            TweenLite.set(el, {
                                backgroundImage:'-ms-radial-gradient(center,circle cover,' + theLuckyColors.top + ' 0%, ' + theLuckyColors.bottom + ' 100%)'
                            });
                        }
                        else if(isFF) {
                            TweenLite.set(el, {
                                backgroundImage:'-moz-radial-gradient(center,circle cover,' + theLuckyColors.top + ' 0%, ' + theLuckyColors.bottom + ' 100%)'
                            });
                        }
                        else {
                            TweenLite.set(el, {
                                backgroundImage:'radial-gradient(circle,' + theLuckyColors.top + ', ' + theLuckyColors.bottom + ')',
                                backgroundImage:'-webkit-radial-gradient(circle,' + theLuckyColors.top + ', ' + theLuckyColors.bottom + ')'
                            });
                        }
                    }
                    swirl();
                }
                ColorSwirl(['red','green','#4B0082','#9F00FF','yellow','orange'],'blue',.15);
            }

        },
        stopTheCycle: function() {

        },

        render: function() {
            return (
                <a className="psychedelicon" href={this.props.href} target={this.props.target} onMouseEnter={this.cycleColors} onMouseLeave={this.stopTheCycle}>
                    <i className={"fa fa-" + this.props.icon}></i>
                </a>
            )
        }

    });
    module.exports = Psychedelicon;

So far I have tried to bind "this" to the the element receiving the event:

onMouseEnter={this.cycleColors.bind(this)}

and I got: `'You are binding a component method to the component. React does this for you automatically in a high-performance way, so you can safely remove this call.'

I also tried:

onMouseEnter={this.cycleColors.call(Psychedelicon)}

and onMouseEnter={this.cycleColors.bind(Psychedelicon)}

which both produced no error but did not work

I know that the function otherwise works because when I change

onUpdateParams:[this]

to

onUpdateParams:['.psychedelicon']

The component produces the desired behavior, except that it effects all of the components at the same time (which I need to avoid hence needing to use "this").

I must be missing something. Any help is appreciated.

Answer 1

So I was able to solve my own problem. Here is the code that did the trick:

var React = require('react');
var GSAP  = require('gsap');
var $     = require('jquery')

var Psychedelicon = React.createClass({

    componentDidMount: function() {

        var that = React.findDOMNode(this.refs.psicon);
        $(that).hover(function() {
    //detect device type for Psychedelicon
            var touchPlatforms = ['iPhone', 'iPad', 'iPod', 'Android', 'Linux armv7l', 'WinCE'];
                       isTouch  = false;
                       iDevice  = false;
                       isDroid  = false;
                       plat = navigator.platform;

            if(plat === 'iPhone' || plat === 'iPad' || plat === 'iPod') {
                isTouch  = true;
                iDevice  = true;
            }
            else if (plat === 'Linux armv7l' || plat === 'Android') {
                isTouch  = true;
                isDroid  = true;
            }
            else {
                for (var i = 0; i < touchPlatforms.length; i++) {
                    if (plat === touchPlatforms[i]) {
                        isTouch = true;
                        break;
                    }
                    else {
                        isTouch = false;
                    }
                }
            }

    //sniff the for ie
            var isIE = false
                if (navigator.userAgent.toLowerCase().indexOf('msie') > -1 || navigator.userAgent.toLowerCase().indexOf('trident') > -1) {
                isIE = true
            }

    //sniff for firefox
            var isFF = false
                if (navigator.userAgent.toLowerCase().indexOf('firefox') != -1) {
                isFF = true
            }


    //Begin ColorSwirl on non-touch devices
            if(!isTouch) {
    //Define the Color Sets
                var ColorSwirl = function(colorSet,defaultColor,time) {
    //Pick random color. If the color is the same as the previous one pick blue instead.
                    var storedResult;
                    var randomColor = function(theArray) {
                        var result = theArray[Math.floor(Math.random() * (theArray.length))];
                        if(result === storedResult){
                            return(defaultColor)                        
                        }
                        else {
                            storedResult = result;
                            return(result)
                        }
                    }
    //Pick our colors for the initial state
                    var theLuckyColors = {top:randomColor(colorSet),bottom:randomColor(colorSet)};
    //Start swirling
                    $(that).addClass('swirling');
                    var swirl = function(){
                        if($(that).hasClass('swirling')) {
                            TweenLite.to(theLuckyColors, time, {colorProps:{top:randomColor(colorSet), bottom:randomColor(colorSet)}, onUpdate:colorize, onUpdateParams:[that],onComplete:swirl});
                        }
                    }
    //Detect Browser and Pass Psychedelicon the appropriate radial gradients
                    var colorize = function(el) {
                        if(isIE) {
                            TweenLite.set(el, {
                                backgroundImage:'-ms-radial-gradient(center,circle cover,' + theLuckyColors.top + ' 0%, ' + theLuckyColors.bottom + ' 100%)'
                            });
                        }
                        else if(isFF) {
                            TweenLite.set(el, {
                                backgroundImage:'-moz-radial-gradient(center,circle cover,' + theLuckyColors.top + ' 0%, ' + theLuckyColors.bottom + ' 100%)'
                            });
                        }
                        else {
                            TweenLite.set(el, {
                                backgroundImage:'radial-gradient(circle,' + theLuckyColors.top + ', ' + theLuckyColors.bottom + ')',
                                backgroundImage:'-webkit-radial-gradient(circle,' + theLuckyColors.top + ', ' + theLuckyColors.bottom + ')'
                            });
                        }
                    }
                    swirl();
                }
                ColorSwirl(['red','green','#4B0082','#9F00FF','yellow','orange'],'blue',.15);
            }

        },function() {
            var theLuckyColors = {top:'#FFFFFF',bottom:'#FFFFFF'};
            var stopNow = function(time){
                $(that).removeClass('swirling');
                TweenLite.to(theLuckyColors, time, {colorProps:{top:'#FFFFFF', bottom:'#FFFFFF'}, onUpdate:whiteWash, onUpdateParams:[that]});
            }
            var whiteWash = function(el) {
                    TweenLite.set(el, {
                        backgroundImage:'-ms-radial-gradient(center,circle cover,#FFFFFF 0%, #FFFFFF 100%)',
                        backgroundImage:'-moz-radial-gradient(center,circle cover,#FFFFFF 0%, #FFFFFF 100%)',
                        backgroundImage:'radial-gradient(circle,#FFFFFF,#FFFFFF)',
                        backgroundImage:'-webkit-radial-gradient(circle,#FFFFFF,#FFFFFF)'
                    });
            }
            stopNow(.15);       
        });
    },
    render: function() {
        return (
            <a className="psychedelicon" ref="psicon" href={this.props.href} target={this.props.target} onMouseEnter={this.cycleColors} onMouseLeave={this.stopTheCycle}>
                <i className={"fa fa-" + this.props.icon}></i>
            </a>
        )
    }

})

module.exports = Psychedelicon;

Here is how I got from the problem to the solution:

When I was unable to produce a result by using "call" as was suggested by @Alexander O'Mara, i required jQuery to speed up testing and added the variable

var that = $(this)

to the component's outermost scope, so that I could access the component itself from the scope of the inner functions like so:

//Note that onUpdateParams now references "that" which is equal to "this" in the scope of the actual component.
TweenLite.to(theLuckyColors, time, {colorProps:{top:randomColor(colorSet), bottom:randomColor(colorSet)}, onUpdate:colorize, onUpdateParams:[that],onComplete:swirl});

this failed again so I logged the value of "this" to the console and saw that I was actually referencing the component's constructor and not the rendered output!

I had a look at the docs again and saw that I could reference the rendered output on every render instance by using a reactjs attribute called "refs". I needed only to give the rendered element a "ref" attribute:

render: function() {
        return (
            <a className="psychedelicon" ref="psicon" href={this.props.href} target={this.props.target} onMouseEnter={this.cycleColors} onMouseLeave={this.stopTheCycle}>
                <i className={"fa fa-" + this.props.icon}></i>
            </a>
        )
    }

and reference the ref in my method, which I decided to run out of "componentDidMount" instead.

var that = React.findDOMNode(this.refs.psicon);

Now, everytime I reference "that" I am referencing the rendered element itself (pretty impresive considering it's re-rendering every .15 seconds on mouseover) and everything is peachy!

Answer 2

UPDATE: This answer does not apply to React, but was in response to a more-general previous version of the question.

---

This looks like another argument for not using the onclick attribute, but you could use the call or apply method, and pass this as the first argument.

<div id="foo" onClick="Module.addClass.call(this)"></div>

However you might want to consider using addEventListener or jQuery's event delegation instead.