indexof element in array javascript code example

Example 1: javascript indexOf object value in array

// Get index of object with specific value in array
const needle = 3; // needle
const haystack = [{ id: 1 }, { id: 2 }, { id: 3 }]; // haystack
const index = haystack.findIndex(item => item.id === needle);

Example 2: 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 3: index of value in array

// for dictionary case use findIndex 
var imageList = [
   {value: 100},
   {value: 200},
   {value: 300},
   {value: 400},
   {value: 500}
];
var index = imageList.findIndex(img => img.value === 200);

Example 4: js array get index

var fruits = ["Banana", "Orange", "Apple", "Mango"];
return fruits.indexOf("Apple"); // Returns 2

Example 5: javasript array indexof

var array = [2, 9, 9];
array.indexOf(2);     // 0
array.indexOf(7);     // -1
array.indexOf(9, 2);  // 2
array.indexOf(2, -1); // -1
array.indexOf(2, -3); // 0

Example 6: get array by array of indices js

var resultArr = indexArr.map(i => fruitier[i])