Nodejs Array Filter singleOrNone(filter)

Method Source Code

Array.prototype.singleOrNone = function(filter) {
   var matches = this.filter(filter);
   if (matches.length > 1) {
      throw new Error("Expected 1 but found many");
   }//  w  ww  . j av a  2  s  .co  m
   if (matches.length == 0) {
      return null;
   }

   return matches[0];
}

Related

1. filterEmpty()

   Array.prototype.filterEmpty = function ()
       var arr = this;
       var i = arr.length;
       while (i--)
           if (arr[i] instanceof Array)
               arr[i] = arr[i].filterEmpty();
   ...
   

2. filterSyncasync (callback, thisArg)

   Array.prototype.filterSync = async function (callback, thisArg) {
     let filterResult = await Promise.all(this.map(callback))
     return this.filter((_, index) => filterResult[index])
   

3. filterUnique()

   Array.prototype.filterUnique = function() {
       'use strict';
       var arr = [];
       var orig = this;
       orig.forEach(function(a, i) {
           if (arr.indexOf(a) < 0) {
               arr.push(a);
           } else {
               orig.splice(i, 1);
   ...
   

4. mfilter(fun)

   Array.prototype.mfilter =  function (fun) {
     var filtered = [];
     for(let i = 0; i < this.length; i++) {
       if (fun(this[i], i, this)) filtered.push(this[i]);
     return filtered;
   };
   var returnarr = [1,2,3,4,5,6].mfilter(function(element, index, arr) {
     return element > 5;
   ...
   

5. single(filter)

   Array.prototype.single = function(filter) {
     var matches = this.filter(filter);
     if (matches.length == 0) {
       throw new Error("Expected 1 but found 0");
     if (matches.length > 1) {
       throw new Error("Expected 1 but found many");
     return matches[0];
   ...