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POWhat is the explanation for these bizarre JavaScript behaviours mentioned in the 'Wat' talk for CodeMash 2012?
 

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  1. POWhat is the explanation for these bizarre JavaScript behaviours mentioned in the 'Wat' talk for CodeMash 2012?
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    <p>The <em><a href="https://www.destroyallsoftware.com/talks/wat">'Wat' talk for CodeMash 2012</a></em> basically points out a few bizarre quirks with Ruby and JavaScript.</p> <p>I have made a JSFiddle of the results at <a href="http://jsfiddle.net/fe479/9/">http://jsfiddle.net/fe479/9/</a>.</p> <p>The behaviours specific to JavaScript (as I don't know Ruby) are listed below.</p> <p>I found in the JSFiddle that some of my results didn't correspond with those in the video, and I am not sure why. I am, however, curious to know how JavaScript is handling working behind the scenes in each case.</p> <pre><code>Empty Array + Empty Array [] + [] result: &lt;Empty String&gt; </code></pre> <p>I am quite curious about the <code>+</code> operator when used with arrays in JavaScript. This matches the video's result.</p> <pre><code>Empty Array + Object [] + {} result: [Object] </code></pre> <p>This matches the video's result. What's going on here? Why is this an object. What does the <code>+</code> operator do?</p> <pre><code>Object + Empty Array {} + [] result [Object] </code></pre> <p>This doesn't match the video. The video suggests that the result is 0, whereas I get [Object].</p> <pre><code>Object + Object {} + {} result: [Object][Object] </code></pre> <p>This doesn't match the video either, and how does outputting a variable result in two objects? Maybe my JSFiddle is wrong.</p> <pre><code>Array(16).join("wat" - 1) result: NaNNaNNaNNaNNaNNaNNaNNaNNaNNaNNaNNaNNaNNaNNaNNaN </code></pre> <p>Doing wat + 1 results in <code>wat1wat1wat1wat1</code>...</p> <p>I suspect this is just straightforward behaviour that trying to subtract a number from a string results in NaN.</p>
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    1. COThe {} + [] is basicaly the only tricky and implementation dependent one, as I explain [here](http://stackoverflow.com/questions/9021109/what-is-in-javascript/9021351#9021351), because it depends on being parsed as an statement or as an expression. What environment are you testing in (I got the expected 0 in Firefow and Chrome but got the "[object Object]" in NodeJs)?
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    2. COI'm running Firefox 9.0.1 on windows 7, and JSFiddle evaluates it to [Object]
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    3. CO@missingno I get 0 in the NodeJS REPL
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