For in Loop JavaScript Code Example

Last Updated On Friday 19th Nov 2021
  • 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.