Advanced Guide to JavaScript typeof Operator

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The typeof operator in JavaScript is used to determine the type of a given value or variable at runtime. While it seems simple at first glance, understanding its quirks and advanced use cases is essential for mastering type checking and handling dynamic behavior in JavaScript.

This guide will dive deep into the advanced aspects of typeof, highlighting how it behaves, the edge cases, and how you can use it effectively in modern JavaScript applications.

Basic Syntax and Usage

The syntax of typeof is straightforward:

typeof operand

Where operand is the value whose type you want to check. typeof returns a string that represents the type of the operand.

Examples:

console.log(typeof 42);              // "number"
console.log(typeof 'Hello World');    // "string"
console.log(typeof true);             // "boolean"
console.log(typeof undefined);        // "undefined"
console.log(typeof {});               // "object"
console.log(typeof function(){});     // "function"
console.log(typeof Symbol());         // "symbol"

The basic types returned by typeof are:

• “undefined” — for undefined values.
• “object” — for objects, arrays, null…