Why JavaScript Statement "ga = ga || []" Works?

Posted by Morgan Cheng on Stack Overflow See other posts from Stack Overflow or by Morgan Cheng
Published on 2010-04-21T03:31:39Z Indexed on 2010/04/21 3:43 UTC
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JavaScript

|

syntax

Below javascript statements will cause error, if ga is not declared.

if (ga)
{
   alert(ga);
}

The error is:

ga is not defined

It looks undeclared variable cannot be recognized in bool expression. So, why below statement works?

var ga = ga || [];

To me, the ga is treated as bool value before "||". If it is false, expression after "||" is assigned to final ga.

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