typeof Operator in JavaScript

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ID: JS-003
Date: [Insert Date]

Content:
The typeof operator in JavaScript is used to determine the type of a value or variable. It returns a string indicating the type of the operand.

Syntax:

typeof operand

Return Values:

"number" for numbers (including NaN).
"string" for strings.
"boolean" for booleans.
"undefined" for undefined values.
"object" for objects, null, and arrays.
"function" for functions.
"bigint" for BigInt values.
"symbol" for symbols.

Examples:

console.log(typeof 42); // "number"
console.log(typeof 'Hello'); // "string"
console.log(typeof true); // "boolean"
console.log(typeof undefined); // "undefined"
console.log(typeof null); // "object" (historical bug)
console.log(typeof {}); // "object"
console.log(typeof []); // "object"
console.log(typeof function() {}); // "function"
console.log(typeof BigInt(123)); // "bigint"
console.log(typeof Symbol('id')); // "symbol"

Common Use Cases:

Type Checking:
Ensure a variable is of the expected type before performing operations.
```
if (typeof value === 'number') {
    console.log('Value is a number');
}
```
Debugging:
Log the type of a variable to debug unexpected behavior.
```
console.log(typeof someVariable);
```

Handling Undefined Variables:
Check if a variable is defined before using it.

if (typeof someVariable === 'undefined') {
    console.log('Variable is undefined');
}

Limitations:

The typeof null returns "object", which is a historical bug in JavaScript.
Arrays are also considered objects, so typeof [] returns "object".

Connections:

Connections:

Sources:

From: Una breve guía a la programación y JavaScript