One Pager Cheat Sheet

• You can convert a number to its text equivalent using number spelling in O(n) time and O(n) space complexity, where n is the number of digits and the number of digits must not exceed 100.
• We can convert the number 123 to a string type to start our operation.
• We need to define units, tens and scales for building the final string, and then divide the number into chunks of 3 digits to account for different scales.
• We iterate through num in O(n) linear time, and convert it to a string of length n for O(n) space complexity.

This is our final solution.

To visualize the solution and step through the below code, click Visualize the Solution on the right-side menu or the VISUALIZE button in Interactive Mode.

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}

var assert = require('assert');

​

/**

 * Convert an integer to its words representation

 *

 * @author McShaman (http://stackoverflow.com/users/788657/mcshaman)

 * @source http://stackoverflow.com/questions/14766951/convert-digits-into-words-with-javascript

 */

function numberToWords(n) {

  var string = n.toString(),

    units,

    tens,

    scales,

    start,

    end,

    chunks,

    chunksLen,

    chunk,

    ints,

    i,

    word,

    words,

    and = 'and';

​

  /* Remove spaces and commas */

  string = string.replace(/[, ]/g, '');

​

  /* Is number zero? */

  if (parseInt(string) === 0) {

    return 'zero';

  }

​

Great job getting through this. Let's move on.

If you had any problems with this tutorial, check out the main forum thread here.