Plus Equals New vs Equals Old Plus New

JavaScript performance comparison

Revision 3 of this test case created by Russell Dempsey


I've always used

foo += bar;

for string concatenation but I'm curious how it performs against

foo = foo + bar;

at high volume.

Preparation code

Benchmark.prototype.setup = function() {
    var a = 'hello';
    var b = ' world, ';

Test runner

Warning! For accurate results, please disable Firebug before running the tests. (Why?)

Java applet disabled.

Testing in unknown unknown
Test Ops/sec
A Plus Equals B
a += b
A Equals A plus B
a = a + b

Compare results of other browsers


You can edit these tests or add even more tests to this page by appending /edit to the URL. Here’s a list of current revisions for this page:


Comment form temporarily disabled.

Add a comment