JavaScript for...in Loop

Key Points:

• The for...in loop helps iterate over the properties of an object.
• Useful for extracting keys or indices, especially in objects and arrays.

Syntax:

for (let key in object) {
  // Code to be executed for each property
}

Example: Iterating over Object Properties:

const person = { name: 'John', age: 30, job: 'Developer' };

for (let key in person) {
  console.log(key + ': ' + person[key]);
}

This loop prints each property and its value in the person object.

Example: Iterating over Array Indices:

const person = { name: 'John', age: 30, job: 'Developer' };

for (let key in person) {
  console.log(key + ': ' + person[key]);
}

This loop prints each index and value in the numbers array.

 

Summary

The for...in loop is a simple way to go through the properties of an object or the indices of an array.