indexof in object 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: using index of on array of objects

arr = [{x: "a", y: 1}, {x: "something", y: 2}]
arr.findIndex(obj => obj.x === "a" && obj.y === 1);

Example 3: 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 4: js index to index

let array = [5, "Foo", 3, "Bar"];
array.slice(2);
// Output = [3, "Bar"]

let string = "Volvo Cars";
string.slice(2);
// Output = "lvo cars"