index of an array javascript code example

Example 1: get index of element in array js

const beasts = ['ant', 'bison', 'camel', 'duck', 'bison'];

console.log(beasts.indexOf('bison'));
// expected output: 1

// start from index 2
console.log(beasts.indexOf('bison', 2));
// expected output: 4

console.log(beasts.indexOf('giraffe'));
// expected output: -1

//*** Thanks to MDN Web Docs ***//
//https://developer.mozilla.org/fr/docs/Web/JavaScript/Reference/Objets_globaux/Array/indexOf

Example 2: js array return only certain positions

const every_nth = (arr, nth) => arr.filter((e, i) => i % nth === nth - 1);
console.log(every_nth([1, 2, 3, 4, 5, 6], 1));
console.log(every_nth([1, 2, 3, 4, 5, 6], 2));
console.log(every_nth([1, 2, 3, 4, 5, 6], 3));
console.log(every_nth([1, 2, 3, 4, 5, 6], 4));

// OUTPUT

[1,2,3,4,5,6]
[2,4,6]
[3,6]
[4]

Example 3: how to get the index of an array in javascript

search = (arr, item) => { return arr.indexOf(item); }

Example 4: indefOf

const beasts = ['ant', 'bison', 'camel', 'duck', 'bison'];

console.log(beasts.indexOf('bison'));
// expected output: 1

Example 5: check items in array javascript

function checkAllEven(arr) {
  return arr.every(function(x){
	 return	x % 2 === 0
	})
}

//using "every" to check every item in array.