Init object in javascript using

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What does “var FOO = FOO || {}” (assign a variable or an empty object to that variable) mean in Javascript? 7 answers

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The || operator returns the left operand if it evaluates as true, otherwise it evaluates and returns the right operand. In other words, a || b a || b is equivalent to a ? a : b a ? a : b except that a is only evaluated once.

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To understand the || operator, let's first look at a fairly basic example. The logical OR operator may be used to provide a default value for a defined variable as follows:

 var bar = false,  
 foobar = 5,  
 foo = bar || foobar; // foo = 5  

In this case, foo will only be assigned the value of foobar if bar is considered falsy. A falsy value could be considered being equal to 0, false, undefined, null, NaN or empty (eg "").

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这会初始化myObj，除非它已经被定义。

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