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Thread: Small question about JavaScript operators in DWT code

  1. #1
    sdouglass is offline Intermediate Member
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    Oct 2005
    Emeryville, CA US
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    Default Small question about JavaScript operators in DWT code

    Hi! Like everybody else I'm very excited about your product and have been going over the code, mostly focusing on DWT at first. I've noticed a couple places where there's a JavaScript operator that I've not seen before. For example:

    59: if (retVal === false)

    34: if (compress !== true)

    Are those equivalent to "==" and "!=" respectively? If not, how are they different? If so, why use them instead of "==" and "!="?

  2. #2
    KevinH's Avatar
    KevinH is offline Expert Member
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    Aug 2005
    San Mateo, CA
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    The === and !== are identity compares (ie check that things are identical without tye conversion) Some more detail below.


    The == and != operators do type coercion before comparing. This is bad because it causes '' == 0 to be true. This can mask type errors.

    When comparing to any of the following values, use the === or !== operators, which do not do type coercion.

    0 '' undefined null false true
    If you want the type coercion, then use the short form. Instead of
    (foo != 0)
    just say
    and instead of
    (foo == 0)

  3. #3
    JeffP is offline Junior Member
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    Oct 2005
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    Check out and see his jslint utility to get used to using this operator in your own code. It only took me a couple of times of running my files thru it and I learned the crockford way..

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