JavaScript typeof operator

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

Here are some examples of using the typeof operator:

console.log(typeof 42); // Output: "number"
console.log(typeof "Hello"); // Output: "string"
console.log(typeof true); // Output: "boolean"
console.log(typeof undefined); // Output: "undefined"
console.log(typeof null); // Output: "object"
console.log(typeof [1, 2, 3]); // Output: "object"
console.log(typeof { name: "John", age: 30 }); // Output: "object"
console.log(typeof function() {}); // Output: "function"

The typeof operator can be used with any value or variable, including numbers, strings, booleans, objects, arrays, functions, and even null and undefined. It returns a string representing the type of the operand.

However, it’s important to note that the typeof operator has some quirks and limitations. For example, it returns "object" for arrays and null, which can be misleading. Also, it treats typeof null as "object" instead of "null", which is a historical mistake in the JavaScript language.

To perform more precise type checking, it’s recommended to use other methods like instanceof, Array.isArray(), or custom type-checking functions.