Is there a JavaScript function that can pad a string to get to a determined length?

Question

I am in need of a JavaScript function which can take a value and pad it to a given length (I need spaces, but anything would do). I found this:

Code:

Answer 1

es7 is just drafts and proposals right now, but if you wanted to track compatibility with the spec, your pad functions need:

1. Multi-character pad support.
2. Don't truncate the input string
3. Pad defaults to space

From my polyfill library, but apply your own due diligence for prototype extensions.

// Tests
'hello'.lpad(4) === 'hello'
'hello'.rpad(4) === 'hello'
'hello'.lpad(10) === '     hello'
'hello'.rpad(10) === 'hello     '
'hello'.lpad(10, '1234') === '41234hello'
'hello'.rpad(10, '1234') === 'hello12341'

String.prototype.lpad || (String.prototype.lpad = function( length, pad )
{
    if( length < this.length ) return this;

    pad = pad || ' ';
    let str = this;

    while( str.length < length )
    {
        str = pad + str;
    }

    return str.substr( -length );
});

String.prototype.rpad || (String.prototype.rpad = function( length, pad )
{
    if( length < this.length ) return this;

    pad = pad || ' ';
    let str = this;

    while( str.length < length )
    {
        str += pad;
    }

    return str.substr( 0, length );
});