JavaScript Equality Table

There is a followup article &quot;Don&#x27;t Make Javascript Equality Look Worse Than It Is&quot;<p>&quot;These posts are fundamentally right about == being poorly designed... but they make things look worse by failing to organize the table.... What a mess! But most of the mess is because of the order of values in the table. By grouping equal values together, you get something more sensible&quot;<p><a href="http://strilanc.com/visualization/2014/03/27/Better-JS-Equality-Table.html" rel="nofollow">http:&#x2F;&#x2F;strilanc.com&#x2F;visualization&#x2F;2014&#x2F;03&#x2F;27&#x2F;Better-JS-Equal...</a>

The rules are fairly simple: <a href="http://www.ecma-international.org/ecma-262/5.1/#sec-11.9.3" rel="nofollow">http:&#x2F;&#x2F;www.ecma-international.org&#x2F;ecma-262&#x2F;5.1&#x2F;#sec-11.9.3</a>

I like the end of the article. &quot;Use three equals unless you fully understand the conversions that take place for two-equals.&quot;<p>Or better said, &quot;Always use 3 equals unless you have a good reason to use 2.&quot;

<p><pre><code> if (2) { console.log(&#x27;yes&#x27;) } &gt; yes &gt; undefined if (2==true) { console.log(&#x27;yes&#x27;) } &gt; undefined </code></pre> I would have thought these would be the same - what&#x27;s the difference between being &quot;truthy&quot; in the first case, and being ==true, as in the second?

Most of these scenarios are mitigated by knowing what types of data are coming into your functions. If you&#x27;re defending against a string being compared to a number, I&#x27;d sooner wonder why you don&#x27;t know whether you have a string or a number in your variable in the first place. What could cause you to attempt to use `[1]`(array containing number 1 as an element) as a boolean? Seems like you should know if a variable contains an array and not true&#x2F;false, and if you don&#x27;t then that&#x27;s a better place to focus your attention.<p>Happy to hear counterexamples though.

It immediately grabbed my attention that they used images for the column labels. Vertical text should be doable with CSS.

This reminds me of Miłosz Kośmider&#x27;s &quot;Zeros in JavaScript&quot; comparison table: <a href="http://zero.milosz.ca/" rel="nofollow">http:&#x2F;&#x2F;zero.milosz.ca&#x2F;</a><p>Essentially the same thing, but covers a few more operations.

All dynamically typed languages with implicit coercion will have similar-looking tables:<p>PHP: <a href="http://www.blueshoes.org/en/developer/php_cheat_sheet" rel="nofollow">http:&#x2F;&#x2F;www.blueshoes.org&#x2F;en&#x2F;developer&#x2F;php_cheat_sheet</a><p>Perl: <a href="http://qntm.org/equality" rel="nofollow">http:&#x2F;&#x2F;qntm.org&#x2F;equality</a><p>Python: <a href="http://i.stack.imgur.com/Ya0Ux.png" rel="nofollow">http:&#x2F;&#x2F;i.stack.imgur.com&#x2F;Ya0Ux.png</a> (I don&#x27;t think all the entries are correct)

Object plus object is not a number :)<p><a href="https://www.destroyallsoftware.com/talks/wat" rel="nofollow">https:&#x2F;&#x2F;www.destroyallsoftware.com&#x2F;talks&#x2F;wat</a>

Interesting, I didn&#x27;t know about `[1] == true`, `[0] == false` family of equalities.<p>Edit: it seems more general, `42 == [42]` etc. holds.<p>Edit: more fun<p><pre><code> ([0])==false &#x2F;&#x2F; true !([0])==false &#x2F;&#x2F; true</code></pre>

Well, at least it&#x27;s got some symmetry to it!

&quot;[] == []&quot; and also with &quot;===&quot; is false. Why they choose not to use these for array comparisons?

Going to the link made my Firefox (34.0.5) allocate over 2 GB of RAM... and then everything stalled to molasses...

Can someone do this table for Go? I&#x27;m just curious to see it.

<i></i>tl;dr<i></i> ignore == and !=, use === and !== instead

i think this table was already posted many times - but this equality table thing never gets boring :D

It leaves out negative zero.

At least it is commutative.

dynamic typing good<p>weak typing bad