Padding Zeros to an Index eg 10 becomes 0010

[Mike Hale]

I am trying to do something like this;

when i = 1 string ="0001"
when i = 10 string = "0010"
etc

When I did a serach I found Xbytor's _zeroPad functon but it only adds 1 zero if less than 10. I can change that with if statements but I thougt I would ask first if there is a better way

Thanks,
Mike

[Andrew]

Heh heh, how many mad ways can we find to do this. How about this one:

var i = 10;
var z = 10000;
var s =( i + z).toString().substr(1);

Andrew

[Andrew]

var i = '10';
var z = '0000';
var s = z.substr(0,z.length - i.length) + i;

This is fun.

Andrew

[Mike Hale]

That works great.

Would you explain how it works incase I need to change the number of leading 0s.

On a grade school level

[Andrew]

The first just adds the numbers as numbers 10010 the converts that to a string then takes off the first character of the string. If they were a string to start with you might have to convert them to a number first, but then you can use the second method whichis entirely string based. The second method can be used with i being a number by converting it to a string first.

alert(Number(10).toString() == '10');

Andrew

[Mike Hale]

Ok, one last question. Do you see anything right off that looks wrong with this function?

Code: Select allfunction zeroPad(i,pad) {
    var z = Math.pow(10,pad)
    var s =( i + z).toString().substr(1);
    return s;
}
alert(zeroPad(23,4))

[Andrew]

You might be safer to use:

var s =(Number( i) + z).toString().substr(1);

Then it will work if i is a number or a string. I'm going to move this to the code snippets forum.

Andrew

[Mike Hale]

In that case I am changing z to this var z = Math.pow(10,Number(pad)) right?

Thanks for all your help with this

Mike

[Andrew]

This is the string version, it is possibly marginally more efficient:

Code: Select allfunction zeropad (n,l) {
   n = n.toString();
   l = Number(l);
   var pad = '0';
   while(n.length < l) {n = pad + n;}
   return n;
}

var n = 10;
var l = 4;


Andrew

[otherthings]

The first several code snippets are potentially dangerous. What if the number you're starting with already has more digits than the maximum? In that case, the first digits will get cut off, e.g. 123456 will become 3456.

Andrew's final code snippet is the only one that behaves correctly in that case. (12 becomes 0012, but 123456 remains 123456).