Some simple help classes (2) -- JAVASCTIPT ARRAY LINQ

This problem is often encountered in the schedule. a js array. We need to find out some qualified class capacities, or find the average class capacity sum in the logarithm group. The general approach is to loop. to add the class to a new set and copy the code var array = []; array. push (1); array. push (2); array. push (3); array. push (4); array. push (5); array. push (6); var whereArray = []; for (var model in array) {if (model <3) {whereArray. push (model) ;}} copy the Code. If more code needs to be queried, We have to write a lot of loops to recall that the List set in C # is similar to Array, but System. linq. the Enumerable extension class provides a lot of Linq extension methods so that we can query the List copy code List like the following code <int> list = new List <int> (); a. add (1);. add (2);. add (3);. add (4);. add (5);. add (6); List <int> copyList = list. where (model => model <3); Can I copy the code and use ctipt pt to make a file with System. linq. the extension class of Enumerable is similar. The answer is yes. we can define the following JavaScript script to copy the code Array. prototype. where = function (func) {var copy = []; for (var model in this) {try {if (func (model) {copy. push (model) ;}} catch (ex) {}}} copy the code and place it on the top of the page. We will be pleasantly surprised to find that Array has a Where method while Javascript. Each class method will add a method to it in prototype, that is, inner. we have added a method to call var array = [1, 2, 3, 4, 5, 6]; var copyArray = array. where (function (model) {return model <1 ;}) we will find that this code has the same effect as the first code, but the code needs to be reduced a lot so that we can use other systems. linq. the common methods in Enumerable are defined one by one to copy the code (function () {/* filter elements that meet the requirements func: (e) =>{ return bool} return Array */Array. prototype. where = function (func) {var copy = []; for (var model in this) {try {if (func (model) {copy. push (model) ;}} catch (ex) {}}/* sum func: (e) =>{ return Number} return Number */Array. prototype. sum = function (func) {var int = 0; for (var model in this) {try {var NaN = func (model); if (isNaN (NaN )) {a + = NaN * 1 ;}} catch (ex) {}} return int ;}/ * gets the first qualified element func: (e) in the set) => {return bool} return e or NULL */Array. prototype. find = function (func) {for (var model in this) {try {if (func (model) {return model ;}} catch (ex) {} return null}) (Array) after the code is copied and defined, the file for storing this JS file is directly dragged to the page every time you use the extension method.