how to return specific array index elements in javascript code example

Example 1: javascript get index of object in array

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

Example 2: how to get the index of an array in javascript

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