JavaScript string connection performance optimization_javascript skills

Copy code The code is as follows:

var str = "hello";
str = "world" ;

Background work:
1) Create a string to store "hello" and make str point to it.
2) Create a string to store "world".
3) Create a string to store the result.
4) Copy the current content in str to the resulting string.
5) Copy world into the result string.
6) Update str so that str points to the result string.
Every time a string is spliced, 2)~6) are repeated in a loop. If repeated hundreds or thousands of times, it will consume a lot of resources and affect performance.
Solution:
Use an Array object to store the string, and then use the join() method to output the result.
Modeled after the StringBuffer class in Java.

Copy code The code is as follows:

function StringBuffer(){
this._strings = new Array;
}
StringBuffer.prototype.append = function (str){
this._strings.push(str);
}
StringBuffer.prototype.toString = function (){
return this._strings.join("");
}

Test performance:
Code 1: Use "=" to concatenate strings

Copy code The code is as follows:

var d = new Date();
var str = "";
for(var i=0;i<10000;i ){
str = "test";
}
var d2 = new Date();
document.writeln(d2.getTime( )-d.getTime());

Code 2: Using StringBuffer

Copy code Code As follows:

var d = new Date();
var str = new StringBuffer();
for(var i=0;i<10000;i ){
str.append("test");
}
var res = str.toString();
var d2 = new Date();
document.writeln(d2.getTime()-d .getTime());

Judging from multiple test results, using StringBuffer can save more than 50% of time.