deep.js is a small plugin that you can include in your projects and libraries. It can easily simulate nested loops, no matter what the depth is. It can be used as an alternative for nested for or forEach loops (see Performance section). It is inspired from itertools.product function in Python.

Normally, 3 nested for loops take up this much space:

for (var i = 0; i < 2; i++) {
    for (var j = 0; j < 3; j++) {
        for (var k = 0; k < 4; k++) {
            console.log(i, j, k)
        }
    }
}

With deep.js, it can turn into a one-liner:

deep([2, 3, 4], (i, j, k) => console.log(i, j, k))

Perhaps you are parsing a 5 dimensional array:

for (var i = 0; i < 2; i++) {
    for (var j = 0; j < 3; j++) {
        for (var k = 0; k < 4; k++) {
            for (var l = 0; l < 3; l++) {
                for (var m = 0; m < 2; m++) {
                    doSomething(arr[i][j][k][l][m])
                }
            }
        }
    }
}

With deep.js,

deep([2, 3, 4, 3, 2],
     (i, j, k, l, m) => doSomething(arr[i][j][k][l][m])
)

According to my computer, it's 40% slower than for. Its performance is similar to forEach , which is 39% slower than for . (See the benchmark in https://jsperf.com/deepfor) Thus, when it comes to performance, it can only be considered as a replacement for nested forEach, not for. However, if the task is not CPU-intensive, this plugin can be effortlessly used instead of classical for.

ffriend's answer in this stackoverflow question