Shoutbox

How do I determine if a variable is empty?

For example, in PHP it is empty($variable), what is it in the script?

Thanks

Some methods:
($variable == null)
or just
(!$variable)

code:

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var myVariable;

if ( typeof myVariable === 'undefined' ) Debug.Trace ( 'Your variable is empty' );
else Debug.Trace( typeof myVariable );

---

Each variable has a "type" if the variable is empty it will be undefined.

This checks if the veriable has been initialized as a specific type. Mattike's post is more correct

To make a function which acts exactly like the empty() function in PHP, you'll have to go a bit further, as stated in the PHP documentation:

quote:

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Source: http://www.php.net/manual/en/function.empty.php

The following things are considered to be empty:

• "" (an empty string)
  
• 0 (0 as an integer)
  
• "0" (0 as a string)
  
• NULL
  
• FALSE
  
• array() (an empty array)
  
• var $var; (a variable declared, but without a value in a class)

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Depending on what you want to do, you can choose which "kind of emptiness" you want to check:

• If it's a number, boolean, undefined or NULL variable, you can simply use if(!variable)
  
• If it's a string, you can compare it to an empty string with if(variable === "")
  
• If it's an array, you can check if it's empty with if(variable.length === 0)
  
• etc...

Mattike: == is the equal operator, not ===.

quote:

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Originally posted by vikke
Mattike: == is the equal operator, not ===.

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=== Is the bitwise-equal operator.

quote:

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Originally posted by matty

quote:

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Originally posted by vikke
Mattike: == is the equal operator, not ===.

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=== Is the bitwise-equal operator.

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Also used to type specificity.
vikke, in php if you evaluate 0==false, the value would be true. Because its not testing the type of operands stored. doing 0===false would make it test the type as well which as matty correctly pointed out, is done by checking equality bitwise

I recommend checking out the PHP.js project site, there are many PHP equivalents posted that are available

http://kevin.vanzonneveld.net/techblog/article/ja...nt_for_phps_empty/

I normally use (!$variable)?

or is this bad practice?

quote:

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Originally posted by Stigmata
I normally use (!$variable)?

or is this bad practice?

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It totally depends of what you want to do with it. If you're working with arrays which may be empty or strings which may equal "0", you're better off with empty(). In normal cases however, (!$variable) will do just fine.