Split a JavaScript string into fixed-length pieces

Question

I would like to split a string into fixed-length (N, for example) pieces. Of course, last piece could be shorter, if original string\'s length is not multiple of N<

Answer 1

See this related question: https://stackoverflow.com/a/10456644/711085 and https://stackoverflow.com/a/8495740/711085 (See performance test in comments if performance is an issue.)

First (slower) link:

[].concat.apply([],
    a.split('').map(function(x,i){ return i%4 ? [] : a.slice(i,i+4) })
)

As a string prototype:

String.prototype.chunk = function(size) {
    return [].concat.apply([],
        this.split('').map(function(x,i){ return i%size ? [] : this.slice(i,i+size) }, this)
    )
}

Demo:

> '123412341234123412'.chunk(4)
["1234", "1234", "1234", "1234", "12"]