How to change the value of an object inside an array - Javascript

Question

const nonsense = [{x: '1'}];
console.log(nonsense.indexOf({x: '1'})); // prints -1

I don't understand why it's printing -1 even though the specified object clearly exists in the array.

Answer 1

If you want to do that, you'll need findIndex

const nonsense = [{x: '1'}];
console.log(nonsense.findIndex(item => item.x === '1')); // prints 0

Answer 2

objects are compared by their reference, not by their values.

object inside nonsense array is a different object from the object you passed to indexOf function even though they have same key-value pairs.

Following code will give you the correct index

const obj = {x: '1'};
const nonsense = [obj];

console.log(nonsense.indexOf(obj));

Answer 3

As, in javaScript the objects are compared by reference, not by the values.

const nonsense = [{x: '1'}];
console.log(nonsense.map(o => o.x).indexOf('1'));

or, probably with better performance for larger arrays:

console.log(nonsense.findIndex(o => o.x ==='1'));