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What is the reason that an empty string evaluates to false in Javascript
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What is the best way to test for an empty string with jquery-out-of-the-box?
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Empty function, what is it?
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Why is True returned when checking if an empty string is in another?
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What's the difference between isset() and array_key_exists()?
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Best way to test for a variable's existence in PHP; isset() is clearly broken
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How do you check if a variable is an array in JavaScript?
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How do I check if my array has repeated values inside it?
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How to check if shapefile is empty using ArcPy?
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PHP: a short cut for isset and !empty?
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Checking to see if one array's elements are in another array in PHP
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Using an if statement to check if a div is empty
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How can I check for an empty/undefined/null string in JavaScript?