Is there a way to implement a StringBuilder in JavaScript

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JavaScript string concatenation
does javascript have a built in stringbuilder class?

As it's known when we do str = str + "123" a new string is created. If we have a large number of concatenations it can be rather expensive. Is there a simple way to implement a StringBuilder in JavaScript?

strings are immutable is JS, what do you mean by string builder ? like in C# ? — mpm, Jan 10 '13 at 14:08
There's a post http://stackoverflow.com/questions/112158/javascript-string-concatenation about string catenation techniques. — Peter Wooster, Jan 10 '13 at 14:10

score 10 · Accepted Answer · edited May 23 '17 at 12:18

10

You can push the parts into an array, and then join it:

var builder = []
builder.push( "some", "123" );
builder.push( "content" );
var str = builder.join("");

This SO question explains it in detail, see also this class

edited May 23 '17 at 12:18

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answered Jan 10 '13 at 14:10

fiz

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I prefer the more concise notation: `var str = ['some', '123', 'content'].join('');` (usually with line breaks between items) – keithjgrant Jan 10 '13 at 14:37

algorhythm · Answer 2 · 2013-01-10T22:56:51.143

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I think, it's never really simple to implement a StringBuilder that is faster than normal string concatenations. And that's obviously the reason for the Builder.

Fill an array an if it's full convert it to string.

edited Jan 10 '13 at 22:56

answered Jan 10 '13 at 14:08

algorhythm

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score 1 · Answer 3 · answered Jan 10 '13 at 14:45

Traditional concatenation in JavaScript is optimal if the strings are static.

var foo = 'a' + 'b' + 'c' + 'd';

this is true in most browsers. string-concatenation

If the strings may be variable according to the program either method is equally efficient.

var foo = ""+Math.random() + Math.random() + Math.random() + Math.random();
var foo = [Math.random(), Math.random(), Math.random(), Math.random()].join('');

the differences are not too great between browsers, but the traditional way seems a little better string-random-concatenation

Is there a way to implement a StringBuilder in JavaScript

3 Answers3