How to create function that takes a numeral (just digits without separators (e.g. 19093 instead of 19, 093) complete with punctuation in javascript?

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Hi Team

I am struggling to Create a function that takes a numeral (just digits without separators (e.g. 19093 instead of 19,093) and returns the standard way of reading a number, complete with punctuation using javascript.

What I have tried:

JavaScript

<pre>function numberWithCommas(x) {
    return x.toString().replace(/\B(?<!\.\d*)(?=(\d{3})+(?!\d))/g, ",");
}

function test(x, expect) {
    const result = numberWithCommas(x);
    const pass = result === expect;
    console.log(`${pass ? "✓" : "ERROR ====>"} ${x} => ${result}`);
    return pass;
}

let failures = 0;
failures += !test(0,        "0");
failures += !test(100,      "100");
failures += !test(1000,     "1,000");
failures += !test(10000,    "10,000");
failures += !test(100000,   "100,000");
failures += !test(1000000,  "1,000,000");
failures += !test(10000000, "10,000,000");
if (failures) {
    console.log(`${failures} test(s) failed`);
} else {
    console.log("All tests passed");
}

Posted 22-Feb-23 2:25am

Gcobani Mkontwana

Updated 23-Feb-23 0:17am

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3 solutions

Solution 1

If you take the log₁₀ of a number, what is returned is the number of digits in the number less one as the integer part:

1           0.000
12          1.079
123         2.090
1234        3.091
12345       4.091
123456      5.092
1234567     6.092
12345678    7.092
123456789   8.092
1234567890  9.092

So, if you take the Math.log10()[^] of your value, you can easily work out the length of the string needed. Then it's just a case of extracting digits and inserting them into the string with the appropriate commas - a loop will do it nicely.

Have a think about it, and you'll see what I mean.

Do bear in mind that not all cultures use comma as the separator, or use a "three spacing" format - India for example uses an asymmetric format: "12,34,567"

Posted 22-Feb-23 3:11am

OriginalGriff

Updated 22-Feb-23 3:14am

v2

Comments

Gcobani Mkontwana 22-Feb-23 20:18pm

@OriginalGriff can you show me a working example based on what i have written? I cant seem to get this right " FAILED: Expected: 'Zero.', instead got: '0'
FAILED: Expected: 'Eleven.', instead got: '11'
FAILED: Expected: 'Fourteen.', instead got: '14'
FAILED: Expected: 'Fifteen.', instead got: '15'
FAILED: Expected: 'Forty-three.', instead got: '43'
FAILED: Expected: 'Fifty.', instead got: '50'
FAILED:

OriginalGriff 23-Feb-23 0:57am

I think you have misread the assignment.
I'd go back and read it again - from the error messages you should be returning a text version of the number: "one", "two", "three", ... "one thousand, seven hundred and twenty two", ... instead of "1", "2", "3", "1,722", ...

That's a very different task if so!

Solution 2

* Convert number to string
   * e.g. 1234567 => "1234567"
* Reverse it
   * => "7654321"
* Insert comma after every third char
   * => "765,432,1"
* Reverse it
   * => "1,234,567"

or
Do it in situ: convert to string, keep counting back 3 chars and add comma
e.g. "1234567" => "1234,567" => "1,234,567"

Posted 22-Feb-23 3:21am

jsc42

Updated 22-Feb-23 3:25am

v2

Comments

Gcobani Mkontwana 22-Feb-23 9:34am

@jsc42 where according from my function must i convert a number to a string? Must i add another function below the test failure that does this conversion? Please advice and show me, so can i understand you clearly.

OriginalGriff 22-Feb-23 10:37am

The only format in which you can store a number with "punctuation" is string: numbers do not have a format, it's only applied when you get to the actual presentation to the user - and that's as a string!

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Andre Oosthuizen · Accepted Answer · 2023-02-23T00:17:00

If I look at your comments above, it seems that your output should be a conversion of a number to its text representation, you need to write a separate function that performs the conversion. If so, please update your question accordingly as it is a little misleading right now. I ran your code in jsfiddle and it worked fine -

const NUMBER_WORDS = {
    0: "Zero",
    1: "One",
    2: "Two",
    3: "Three",
    4: "Four",
    5: "Five",
    6: "Six",
    7: "Seven",
    8: "Eight",
    9: "Nine",
    10: "Ten",
    11: "Eleven",
    12: "Twelve",
    13: "Thirteen",
    14: "Fourteen",
    15: "Fifteen",
    16: "Sixteen",
    17: "Seventeen",
    18: "Eighteen",
    19: "Nineteen",
    20: "Twenty",
    30: "Thirty",
    40: "Forty",
    50: "Fifty",
    60: "Sixty",
    70: "Seventy",
    80: "Eighty",
    90: "Ninety"
};

function numberToText(n) {
    if (n < 0 || n > 999999999) {
        throw new Error("Number out of range");
    }
    if (n in NUMBER_WORDS) {
        return NUMBER_WORDS[n];
    }
    let text = "";
    if (n >= 1000000) {
        text += numberToText(Math.floor(n / 1000000)) + " Million ";
        n %= 1000000;
    }
    if (n >= 1000) {
        text += numberToText(Math.floor(n / 1000)) + " Thousand ";
        n %= 1000;
    }
    if (n >= 100) {
        text += numberToText(Math.floor(n / 100)) + " Hundred ";
        n %= 100;
    }
    if (n > 0) {
        if (text !== "") {
            text += "and ";
        }
        if (n in NUMBER_WORDS) {
            text += NUMBER_WORDS[n];
        } else {
            text += NUMBER_WORDS[Math.floor(n / 10) * 10] + " ";
            text += NUMBER_WORDS[n % 10];
        }
    }
    return text.trim();
}

To use this function with the input numbers in your above code, you can call numberToText() on each number and log the result to the console -

console.log(numberToText(0));        // "Zero"
console.log(numberToText(100));      // "One Hundred"
console.log(numberToText(1000));     // "One Thousand"
console.log(numberToText(10000));    // "Ten Thousand"
console.log(numberToText(100000));   // "One Hundred Thousand"
console.log(numberToText(1000000));  // "One Million"
console.log(numberToText(10000000)); // "Ten Million"