javascript convert number with leading zero to string it change the decimal number to octal

Question

I try to convert a number with leading zero. JavaScript interpret the number with leading zero as octal number. But I would like to convert the number to string as decimal number and preserve the leading zero. Any idea?

<!DOCTYPE html>
 <html>
 <body>

<p>Click the button to display the formatted number.</p>

<button onclick="myFunction()">Try it</button>

<p id="demo"></p>

<script>
    function myFunction() {
    var num = 015;

    var n = Number(num).toString();
    document.getElementById("demo").innerHTML = n;
}
</script>

</body>
</html>

a numeric literal with a leading zero and no digits greater than 7 will always be interpreted as an octal ... so don't do that with literals — Jaromanda X, Dec 29 '16 at 02:26
The num field is a input field, sometime there is leading zero in the field. — CK8, Dec 29 '16 at 02:40
no, in the code you posted, the num **var** is an octal literal. Perhaps you should've posted the actual code, and explained that "sometimes the input field has a leading zero" - because you'd want to parseInt(stringValue, 10) to ensure the number is considered to be decimal rather than octal — Jaromanda X, Dec 29 '16 at 02:44
For padding a number with leading zeros, see [*Pad a number with leading zeros in JavaScript*](http://stackoverflow.com/questions/10073699/pad-a-number-with-leading-zeros-in-javascript). — RobG, Dec 29 '16 at 02:44

score 1 · Answer 1 · answered Dec 29 '16 at 02:25

1

try below code

function pad(num, size) {
        var s = num + "";
        while (s.length < size) s = "0" + s;
        return s;
    }
    document.getElementById("demo").innerHTML = pad(15, 4);

output: 0015

answered Dec 29 '16 at 02:25

ravikumar533

24
3

It failed when there is leading zero in the number. for example : – CK8 Dec 29 '16 at 02:31
Of course it does, because that would be an octal literal. As the **actual** source of the number is an input value according to a later comment of yours, you would call `pad` ... `pad(parseInt(inputElement.value, 10), 4);` - where `inputElement` is a **var** that contains the input element that you wish to process the value of – Jaromanda X Dec 29 '16 at 02:49
when I try pad(parseInt(num.value, 10),4) it return NaN – CK8 Dec 29 '16 at 03:03
You can try pad(parseint(num.value),4) – ravikumar533 Dec 29 '16 at 03:33
Thanks, when I try pad(parseInt(num.value),4) it return NaN – CK8 Dec 29 '16 at 03:48
pad(parseInt(num),4) – ravikumar533 Dec 29 '16 at 04:03
when I try pad(parseInt(num),4) it return 0013 – CK8 Dec 29 '16 at 07:42

Joe Yichong · Answer 2 · 2016-12-29T03:10:26.007

0

The parseInt() and parseFloat() functions parse a string until they reach a character that isn't valid for the specified number format, then return the number parsed up to that point. However the "+" operator simply converts the string to NaN if there is an invalid character contained within it. Just try parsing the string "10.2abc" with each method by yourself in the console and you'll understand the differences better.

+"42"; // 42
+"010"; // 10
+"0x10"; // 16

a = "0042";
alert(typeof +a); // number
alert(+a); // 42

edited Dec 29 '16 at 03:10

answered Dec 29 '16 at 02:50

Joe Yichong

615
4
8

when I try parseInt(015,10).toString it return 13 – CK8 Dec 29 '16 at 03:11
Thanks, Sorry the issue was a is number with leading 0 for example a=042. and a is not string if I do – CK8 Dec 29 '16 at 03:21
var a=042; if I do alert(+a) it return 13 – CK8 Dec 29 '16 at 03:25
Sorry I meant var a=015 if I do alert(+a) it return 13. – CK8 Dec 29 '16 at 03:30
a number with a leading 0 will always be treated as an octal in JS, so you need to use a string instead, which will be converted to a decimal number if you put a "+" operator before it. – Joe Yichong Dec 29 '16 at 03:48
Y.C. I I try var a=015 alert(String(+a)); it return NaN; – CK8 Dec 29 '16 at 03:55
Y.C. if I try var a=015; alert(String(+a)); // NaN – CK8 Dec 29 '16 at 03:59
@CK8 var a=015; alert(+a); // 13 var a="015"; alert(+a); // 15 – Joe Yichong Dec 29 '16 at 04:04
But var a = 015 is given from other result, I can't change to var a="015". How to change from number to string with leading zero with octal to decimal conversion? – CK8 Dec 30 '16 at 03:00
Sorry I meant how to change a number to string with leading zero without octal to decimal conversion? – CK8 Dec 30 '16 at 03:02

javascript convert number with leading zero to string it change the decimal number to octal

2 Answers2