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How to check the data type of a variable in JavaScript

Variables and Typesjs types, primitives, typeof, types

instanceof operator in JavaScript checks if an object is an instance of a constructor, useful for distinguishing arrays from objects. Cross-context issues arise with iframes, where instanceof may fail. Combining instanceof with constructor checks enhances reliable type detection across environments.

Standard Objects: String

How to check if a value is a string in JavaScript

Standard Objects: Stringjs string, string, typeof, validation

Robust JavaScript string validation for edge cases like null and undefined. The typeof check prevents TypeError. Use trim() and length to handle empty or whitespace strings. Explicit checks avoid truthiness traps with String objects, essential for user input and API data.