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Editorial Team
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Asked: 2026-05-22T22:47:51+00:00

this code in book jQuery in action page 99 Why he wrote this line

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this code in book jQuery in action page 99

Why he wrote this line

var current = this;

    <!DOCTYPE html>
<html id="greatgreatgrandpa">
    <head>
        <title>DOM Level 0 Bubbling Example</title>
        <link rel="stylesheet" type="text/css" href="../styles/core.css"/>
        <script type="text/javascript" src="../scripts/jquery-1.4.js"></script>
        <script type="text/javascript" src="../scripts/jqia2.support.js"></script>
        <script type="text/javascript">
            $( function() {
                $('*').each( function() {
                    var current = this;
                    this.onclick = function(event) {
                        if (!event)
                            event = window.event;
                        var target = (event.target) ?
                        event.target : event.srcElement;
                        say('For ' + current.tagName + '#'+ current.id +
                        ' target is ' +
                        target.tagName + '#' + target.id);
                    };
                });
            });
        </script>
    </head>
    <body id="greatgrandpa">
        <div id="grandpa">
            <div id="pops">
                <img id="example" src="example.jpg" alt="ooooh! ahhhh!"/>
            </div>
        </div>
    </body>
</html>
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1 Answer

  1. Editorial Team

    He did that so that the this value could be preserved and used inside a nested lexical scope. Each function call to any function involves (internally) setting this to refer to some object, based on the details of the invocation. Thus, inside a nested function (a function declared inside another function, as in this case), should there be a need to refer to the “outer” value of this, well, there’s a problem: this, in that nested context, will have been set to refer to something else (not necessarily, but possibly). By “capturing” this in the outer context, that inner code will be able to refer to it freely.

    That’s a pretty good book by the way; I used to work with one of the authors (Bear) 🙂

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