Nodejs Array Find by Index findIndex(fn, v)

Method Source Code

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;
            }//from  w  w  w.  j  a va 2s .c  o  m
            continue;
        }
        if (isV) {
            if (this[i] && this[i][fn] === v) {
                return i;
            }
            continue;
        }
        if (this[i] === fn) {
            return i;
        }
    }
    return -1;
};

Related

1. findIndex(callback)

   '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;
   ...
   

2. findIndex(obj)

   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;