[Solved] For loop is too slow

Question

You should do a string interpolation or create an Array and then push the values to it.

In the end, you would append the entire string, or use the Array.prototype.join to turn it in a string.

The for loop is fast, the problem there is the I/O. Take a look at the example below:

var Combinatorics = require('js-combinatorics');
var fs = require('fs');

var cp = Combinatorics.cartesianProduct(
  ["4", "@", "/\\", "/-\\", "^", "∂", "λ", "α", "(!", "Z", "α"],
  ["1²", "2", "?", "P\\", "[\"/_", "l\"/_", "|-", "|2", "|?", "®", "12", "/2", "I2", "|^", "|~", "(r)", "|`", "l2", "Я", "ʁ", "я"],
  ["#", "(-)", ")-(", "/-/", "4", "<~>", "[-]", "\\-\\", "]-[", "]~[", "{-}", "{=}", "|-|", "|~|", "}{", ":-:", "}-{", "н"],
  ["!", "'", "1", "[]", "][", "|", "¦", "¡", ":", "]", "ι"],
  ["&", "3", "€", "£", "ë", "[-", "|=-", "ə", "ε"]
);

fs.appendFile('./output.txt', cp.toArray().join('\n'), function(error) {
  if (error)
    console.log('Error writing ' + error);
});

Note: another thing I did here was to cache the cp.toArray() into a variable, so you don’t need to call it once per loop iteration. Doing the both things (write to the file only once, and calling .toArray() only once either, you’ll have a much better performance, completely sure.

UPDATE

I’ve just realized you don’t need a loop at all, since the only thing you’re doing is concatenating a \n for each word you have, and you can do that by calling the Array.prototype.join method.

Accepted Answer