Nodejs Array Last Index lastIndexOf(elem, from)

Method Source Code

Array.prototype.lastIndexOf = function(elem, from) {
   if (from == null) {
      from = this.length - 1;//from   ww w  .  j av  a  2 s  .c o  m
   } else if (from < 0) {
      from = Math.max(0, this.length + from);
   }
   
   for (var i = from; i >= 0; i--) {
      if (this[i] === elem) {
         return i;
      }
   }
   
   return -1;
};

Related

1. lastIndex(searchElement)

   Array.prototype.lastIndexOf = function lastIndexOf(searchElement) {
     if (!(this instanceof Object)) {
       throw new TypeError(this + 'is not an object');
     var
     array = this,
     arrayIsString = array instanceof String,
     length = array.length,
     index = 1 in arguments ? Number(arguments[1]) || 0 : length - 1;
   ...
   

2. lastIndexOf(e)

   Array.prototype.lastIndexOf = function (e) {
       for (var i = this.length - 1, j; j = this[i]; i--) {
           if (j == e) { return i; }
       return -1;
   

3. lastIndexOf(elt /*, from*/)

   Array.prototype.lastIndexOf = Array.prototype.lastIndexOf || function(elt )  {
       var len = this.length;
       var from = Number(arguments[1]);
       if (isNaN(from)) {
           from = len - 1;
       } else {
           from = (from < 0)
               ? Math.ceil(from)
               : Math.floor(from);
   ...
   

4. lastIndexOf(item)

   Array.prototype.lastIndexOf = function(item){
     var lastIndex = -1;
     for (var i=0; i<this.length; i++){
       if (this[i] === item){
         lastIndex = i;
     return lastIndex;
   

5. lastIndexOf(o)

   Array.prototype.lastIndexOf = function (o) {
       var index = this.length;
       for (; index >= 0; index--) {
           if (index in this && this[index] === o)
               return index;
       return -1;
   };
   

6. lastIndexOf(searchElement, fromIndex)

   Array.prototype.lastIndexOf = function(searchElement, fromIndex) {
     if (!fromIndex || !isFinite(fromIndex)) {
       fromIndex = this.length - 1;
     for (var i = fromIndex; i >= 0; --i) {
       if (this.hasOwnProperty(i) && this[i] === searchElement) {
         return i;
     return -1;