Simulation of common java classes in JS Advanced Programming

Preface

Have you ever encountered this situation: You want to splice a long string during javascript programming. If you still use the "+" Operator for processing, it means you are really amateur; maybe you will think that there is a class called StringBuilder in java specifically used to process String concatenation. Is there a similar class in javascript? Unfortunately, javascript does not provide similar classes.

It is the most important thing to think of using StringBuilder. if Javascript is not provided, we can write one by ourselves. Then, store the StringBuilder class in your own js code library (A. js file). In the future, use similar functions to directly introduce a js file.

Js is a very flexible language. We can use native js to simulate many classes in java, and then put these "classes" (actually functions) into one. you can use the js file as your own code library.

Next I will give you some examples to illustrate how to use js to simulate common java classes.

Practice

StringBuilder

/* StringBuilder String concatenation class */function StringBuilder () {this. str_array = new Array ();} // Add the append method StringBuilder for it. prototype. append = function (data) {this. str_array.push (data); return this;} // Add the toString method to StringBuilder. prototype. toString = function () {return this. str_array.join ('');}

Example

Var builder = new StringBuilder (); var name = "wh"; builder. append ('this blog is '). append (name ). append ('write'); alert (builder. toString ());

HashMap

/* HashMap class */function HashMap () {this. entryArray = new Array ();} // put function HashMap. prototype. put = function (key, value) {var obj = this. get (key); if (obj = null) {this. entryArray. push ({key: key, value: value, getKey: function () {return key ;}, getValue: function () {return value ;}});} else {for (var index in this. entryArray) {if (this. entryArray [index]. key = key) {this. entryArray [index]. value = value ;}}// get function HashMap. prototype. get = function (key) {var value = null; for (var index in this. entryArray) {if (this. entryArray [index]. key = key) {value = this. entryArray [index]. value; break ;}} return value ;}// clear function HashMap. prototype. clear = function () {this. entryArray = new Array ();} // putAll function HashMap. prototype. putAll = function (map) {if (map instanceof HashMap) {for (var index in map. entryArray) {this. put (map. entryArray [index]. key, map. entryArray [index]. value) ;}}// entrySet function HashMap. prototype. entrySet = function () {return this. entryArray;} // keySet function HashMap. prototype. keySet = function () {var keyArray = new Array (); for (var index in this. entryArray) {keyArray. push (this. entryArray [index]. key);} return keyArray;} // values Function HashMap. prototype. values = function () {var valueArray = new Array (); for (var index in this. entryArray) {valueArray. push (this. entryArray [index]. value);} return valueArray ;}

We can see from the above

Use [], {}, and other existing data structures to store data. The json data structure formed by [] + {} can simulate various data structures;

Define a function as a "class", such as StringBuilder, which requires a Data Structure to store data.

Add methods on the prototype object of the class, such as append

It's that simple. Have you learned it?