# Filling objects with a loop in JavaScript

Objects can also be filled with data in loops. Let's look at an example. Let's say we have two arrays:

`let keys = ['a', 'b', 'c', 'd', 'e']; let values = [1, 2, 3, 4, 5];`

Let's use them to make an object by taking the keys for this object from the first array, and the values ​​from the second. To do this, we will start the loop and in the loop we will form our object:

`let obj = {}; for (let i = 0; i <= 4; i++) { let key = keys[i]; let value = values[i]; obj[key] = value; } console.log(obj);`

It is not necessary to enter variables for the key and value, you can just do this:

`let obj = {}; for (let i = 0; i <= 4; i++) { obj[keys[i]] = values[i]; } console.log(obj);`

Two arrays are given: the first with the names of the days of the week, and the second with their ordinal numbers:

`let arr1 = ['mon', 'tue', 'wed', 'thu', 'fri', 'sat', 'sun']; let arr2 = [1, 2, 3, 4, 5, 6, 7];`

Using a loop, create an object whose keys will be the names of the days, and the values will be their numbers.

Given an object:

`let obj = {a: 1, b: 2, c: 3, d: 4, e: 5};`

Loop through this object and write to the new object those elements that are even numbers.

Given an object:

`let obj = {a: 1, b: 2, c: 3, d: 4, e: 5};`

Iterate over this object and create a new object so that its keys are the elements of the old object and its values are the keys of the old object.

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