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POWhy doesn't console.log() take a snapshot of the passed variables?
 

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    <p>I've ran into some really weird behavior with javascript today. I think I got it somehow figured out now, but I'd like to know if what I think is going on is really happening or if there is some other magic involved. So this is my code:</p> <pre><code> var SomeObject = {}; SomeObject.foo = function(a, b) { var baz = this.bar(a, b); console.log(baz); console.log(baz.left); SomeObject.magicalStuff(baz); }; SomeObject.bar = function(a, b) { return {left: a-b, top: b-a}; }; SomeObject.magicalStuff = function(position) { position.left = 0; }; SomeObject.foo(100, 50); </code></pre> <p><a href="http://jsfiddle.net/UNWEp/" rel="noreferrer">The code at jsFiddle</a></p> <p>The output of this is something like (depending on the browser):</p> <pre><code>&gt; Object 50 </code></pre> <p>If you expand the "Object" (in Chrome, Safari or Firefox (Firebug) what you get is:</p> <pre><code>&gt; Object left: 0 top: -50 </code></pre> <p>Whereas I would expect:</p> <pre><code>&gt; Object left: 50 top: -50 </code></pre> <p>What I think is going on is that console.log() really just "posts" a reference to the console, which gets read once you click on the "expand" symbol. But doesn't that kind of defeat the purpose of console.log() as a debugging instrument? I always expected console.log() to "snapshot" the stuff I pass to it. It is really surprising to see a statement which comes after the actual console.log() change the output of that very console.log() call.</p> <p>Or is there something else going on?</p> <p><strong>Edit:</strong> I'm also wondering if there is a sound reason for browser developers to implement console.log like this (I guess there is one, otherwise it wouldn't be consistent across major browsers).</p>
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    1. COSee https://bugs.webkit.org/show_bug.cgi?id=35801
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      1. USRoatin Marth
    2. CO@Roatin Marth: I see. But why do they say: "We can't clone object upon dumping it into the console". What technical difficulties occur that I am not able to see? :)
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    3. COThis is often seen when you try to log an event, since all events are a single object, you're usually looking at the latest mousemove event.
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      1. USJuan Mendes
 

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