Most efficient way to concatenate strings in JavaScript?

In JavaScript, I have a loop that has many iterations, and in each iteration, I am creating a huge string with many += operators. Is there a more efficient way to create a string? I was thinking about creating a dynamic array where I keep adding strings to it and then do a join. Can anyone explain and give an example of the fastest way to do this?

Seems based on benchmarks at JSPerf that using += is the fastest method, though not necessarily in every browser.

For building strings in the DOM, it seems to be better to concatenate the string first and then add to the DOM, rather then iteratively add it to the dom. You should benchmark your own case though.

(Thanks @zAlbee for correction)

I have no comment on the concatenation itself, but I'd like to point out that @Jakub Hampl's suggestion:

For building strings in the DOM, in some cases it might be better to iteratively add to the DOM, rather then add a huge string at once.

is wrong, because it's based on a flawed test. That test never actually appends into the DOM.

This fixed test shows that creating the string all at once before rendering it is much, MUCH faster. It's not even a contest.

(Sorry this is a separate answer, but I don't have enough rep to comment on answers yet.)

Three years past since this question was answered but I will provide my answer anyway :)

Actually, accepted answer is not fully correct. Jakub's test uses hardcoded string which allows JS engine to optimize code execution (Google's V8 is really good in this stuff!). But as soon as you use completely random strings (here is JSPerf) then string concatenation will be on a second place.