JSFiddle - React, Tailwind, and code Playground

by adelura

JavaScript

var a = [3, 5, 60, 40, 60];
var checker = function (elem) {
    return (elem == 60);
};
debugger;
var index = getIndex(a, checker);

alert(index); // 2

function getIndex(arr, checker) {
    var max = arr.length;
    for (var i = 0; i < max; i++) {
        var valid = checker(arr[i]);
        if (valid) {
            return index;
        }
    }
    return -1;
}