JavaScript Reference
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Quick Reference

The Array keys() method returns an array iterator object containing the keys of a specified array.

<!-- html element to place output -->
<p id='my_cars'></p>
// array
let cars = ['Lamborghini', 'Ferrari', 'Maserati', 'Alfa Romeo'];

// get the array keys
let car_keys = cars.keys();

// cycle through the keys and output them to the HTML element
let text = '';

for (let x of car_keys) {
  text += x + '<br>';
}

document.getElementById('my_cars').innerHTML = text;

The way this works (see Syntax section below):

  • The keys() method cycles through the array finding each key from the key/value pair

Note

Arrays count starting from zero NOT one. So item 1 is position [0], item 2 is position [1], and item 3 is position [2] … and so on.

Output

0
1
2
3

Syntax

array.keys()

JavaScript Notes:

  • When using JavaScript, single or double quotation marks are acceptable and work identically to one another; choose whichever you prefer, and stay consistent
  • JavaScript is a case-sensitive language; firstName is NOT the same as firstname
  • Arrays count starting from zero NOT one; so item 1 is position [0], item 2 is position [1], and item 3 is position [2] … and so on
  • JavaScript variables must begin with a letter, $, or _
  • JavaScript variables are case sensitive (x is not the same as X)
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