如何在输入值之前递归加数字

Question

This is probably very much a newbie question -- but i can't figure it out.

I have an input text with minlegth 9, and I have to do something like this:

If the user types only one number, I have to add some "0" before this number to reach value.length == 9

Example:
123 => 000000123

I'm using Angular 2 input forms and a pipe to transform the result.

Can anyone help?

---

Here i've found the solution:

transform(val) {
        var standardLength = "000000000";
        return (standardLength + val).slice(-standardLength.length);
    }

Thanks to everyone!

Answer 1

number=("0".repeat(9)+number).substr(-9);

只需将其应用于更改后的输入值。

Answer 2

If the length you want is always static (here 9), this is the easiest method.

 num = [1, 11, 111, 1111, 11111]; for (var i = 0; i < 5; i++) { console.log(("000000000" + num[i]).substr(-9,9)); } 

---

Hope this helps!

Answer 3

Your method is not optimal.

You can use the Slice() method to put into your string whatever you want.

IE:

('0' + '').slice(-2)

Answer 4

function pad(num, size) {
     var s = num+"";
     while (s.length < size) s = "0" + s;
     return s;
}

// usage
pad(123, 9)

Answer 5

transform(val){
    let zeros = "000000000";
    return zeros.concat(val).slice(Math.min(val.toString().length * -1,-9));
}