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Javascript check if a variable is set

Typically, I check if a variable is set with something like this:

if (variable !== '') {

   do something...

}

I know that there are other methods for testing type variables typeof, but I see no advantage - is this an appropriate way to check if a variable is set? Are there any issues with this that I should know about?

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5 answers

Two reasons:

1) What if the variable is set by entering the contents of an empty input field?

if(someScenario){
    var variable = $('empty-box').val(); }

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, true:

  • undefined
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  • 0

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coffeescript, " " : http://coffeescript.org/

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This can be very subjective, but my recommendation is to avoid the code that needs to check whether a variable is set (aot has some value or type).

Consider this snipplet

var a=false;
if (some_condition) a="Blah";
if (typeof(a)=='string') ....
if (a===false) ...

this ensures that ait is always set, keeping it easily differentiable from '', nullor0

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