Equality and Inequalities in JS and PHP

It’s 2015, and from time to time I still see a lot of == peppered throughout codebases that I work with, and just wanted to share a few posts that might change your mind =)


=== and its complement !== and should be used like 99% of the time because it is faster and more accurate.

> 0 == "0"
< true
> 0 === "0"
< false
> 0 == false
< true
> "0" == false // really?
< true
> !!"0"
< true
> !"0"
< false
> "0" === false
< false

There are more perverse and mind-bending examples that are out there, but I’ll leave you with those for now.

As you can see, the former == does type coercion, which is lazy way of doing comparisons without casting data explicitly, and can find yourself in hot water down the line. The latter === does type checking first, and then checks equality of the values.

Protip #1: If you want to test a JS expression or figure out some syntax really quickly, just open your JS console in the browser inspect tool.

Protip #2: If testing for something truthy or falsy, a nice trick is to just do use the ! operator twice (!!). As can be seen above, JS treats non-empty strings as a truthy (yet, strangely, "0" == false)

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26 February 2015


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