How can I check for an empty/undefined/null string in JavaScript?

How can I check for an empty/undefined/null string in JavaScript?

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Is there a standard function to check for null, undefined, or blank variables in JavaScript?

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How can I determine if a variable is 'undefined' or 'null'?

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What is the difference between null and undefined in JavaScript?

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Why is null an object and what's the difference between null and undefined?

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How do I check for null values in JavaScript?

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JavaScript checking for null vs. undefined and difference between == and ===

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How to check for an undefined or null variable in JavaScript?

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Check if object exists in JavaScript

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How to check null objects in jQuery

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Why `null >= 0 && null <= 0` but not `null == 0`?

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What reason is there to use null instead of undefined in JavaScript?

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Why is there a `null` value in JavaScript?

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When is null or undefined used in JavaScript? [duplicate]

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Is it better to return `undefined` or `null` from a javascript function?

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