JSFiddle - React, Tailwind, and code Playground

JavaScript

var arr = new Array({
    x: 1,
    y: 2
}, {
    x: 3,
    y: 4
});

function myIndexOf(o) {

    for (var i = 0; i < arr.length; i++) {
        if (arr[i].x == o.x && arr[i].y == o.y) {
            return i;
        }
    }
    
    return -1;
}

alert(myIndexOf({x:3, y:4}));