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For in Loop JavaScript Code Example

Last Updated on Wednesday 5th Oct 2022
  • for in loop iterates through all the properties of a particular object.
  • It is Special loop beacuse you can pair it up with array.
					for (let variable in obj) {
    // do some stuff here

  • It will loop through the properties of an array just like it did with the properties of an object.
  • The for-in loops provide us the most straightforward way to loop over object keys and values.

Example 1

					let Captains = {
    "England": "Harry Kane",
    "Italy": "Giorgio Chiellini",
    "Germany": "Manuel Neuer"

for (let name in Captains) {
    console.log(name, ':', Captains[name]);

  • In this Example , the for in loop tends to iterate the object.
  • With Each Iteration it returns the key and uses the key to access the specific value of that key that is object Captains.
					// England : Harry Kane
// Italy : Giorgio Chiellini
// Germany : Manuel Neuer


Example 2

					let books = ["Fist of the North Star", "Tokyo Ghoul", "Berserk"]

for (let book in books) {
    console.log(book, ":", books[book]);

					// 0 : Fist of the North Star
// 1 : Tokyo Ghoul
// 2 : Berserk


Example 3

					let a = [];

let array = ['a', 'b', 'c', 'd'];

for (let index in array) {
    a += array[index];

console.log(a) // abcd

  • When using with arrays, the order of is independent of implementation.
  • You Cannot access the values of the array in order that you except.