Improving the code to turn a string into an array of numbers?

Question

I have a string of numbers, like "31654918562314", and I want to convert it into an array of integers. The code I've written is:

string source = "31654918562314";
int[] numbers = new int[source.Length];
for (int i = 0; i < source.Length; i++)
{
    numbers[i] = Convert.ToInt32(source.Substring(i, 1));
}

What improvements can I apply on this code? Is it the best ultimate code I can get to?

Note: I'm using C#. However, I also should implement this code in JavaScript.

Answer 1

I'm partial to using LINQ here. Jon has a point there on the conversion.

var str = "31654918562314";
var numbers = str.Select(c => c - '0').ToArray();

Answer 2

The most efficient code would be to use a plain loop and get the numerical value from the character code:

string source = "31654918562314";
int[] numbers = new int[source.Length];
for (int i = 0; i < source.Length; i++) {
  numbers[i] = source[i] - '0';
}

In Javascript you would use the charCodeAt method to do the same:

var source = '31654918562314';
var numbers = new Array(source.length);
for (var i = 0; i < source.length; i++) {
  numbers[i] = source.charCodeAt(i) - 48;
}

A performance test shows that using charCodeAt in a loop is 10-30 times faster than using a regular expression and parseInt: http://jsperf.com/string-to-array-of-numbers

Answer 3

Javascript

var arr = [];
var matches = "54321".match(/\d/g);
for (var index = 0; index < matches.length; ++index) {
    arr.push(parseInt(matches[index], 10));
}

live demo

Using map() method:

var arr = "54321".match(/\d/g).map(function(m){
    return parseInt(m, 10);
});

live demo