Nodejs Utililty Methods Array Find by Index

'use strict';
Array.prototype.findIndex = Array.prototype.findIndex || function(callback) {
  if (this === null) {
    throw new TypeError('Array.prototype.findIndex called on null or undefined');
  } else if (typeof callback !== 'function') {
    throw new TypeError('callback must be a function');
  var list = Object(this);
  var length = list.length >>> 0;
...

Array.prototype.findIndex = function(fn, v) {
    var isFN = typeof(fn) === 'function';
    var isV = v !== undefined;
    for (var i = 0, len = this.length; i < len; i++) {
        if (isFN) {
            if (fn(this[i], i)) {
                return i;
            continue;
...

Array.prototype.findIndex = function (obj) {
  for (var i = 0, imax = this.length; i < imax; i++) {
    var ectypeObj = this[i];
    var ectypeObjLength = 0, successLength = 0;
    for (var k in ectypeObj) {
      ectypeObjLength += 1;
      if (ectypeObj[k] === obj[k]) {
        successLength += 1;
    if (ectypeObjLength === successLength) {
      return i;
  return -1;