JavaScript: Distinguishing Null vs. Undefined and Comparing with == vs. ===
Checking for Null and Undefined
Checking for Null:
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Strict comparison: if (a === null)
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Loose comparison: if (a == null) (Caution: Will also return true for undefined)
Checking for Undefined:
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Type comparison: if (typeof a === "undefined")
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Strict comparison: if (a === undefined)
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Loose comparison: if (a == undefined) (Caution: Will also return true for null)
Difference Between Null and Undefined
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Undefined: Default value of uninitialized variables, omitted function arguments, and missing object properties. Denotes an "absence".
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Null: Specifically represents an empty object reference.
Difference Between == and ===
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== (Loose Equality): Performs type coercion to equate values (e.g., "1" == 1 is true).
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=== (Strict Equality): Compares both value and type. Returns false if types differ (e.g., "1" === 1 is false).
Note: Strict comparison (===) is recommended for type-safe comparisons and avoiding unexpected results from type coercion.
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