var lpad = require( '@stdlib/string/base/left-pad' );

Left pads a string such that the padded string has a length of at least len.

var str = lpad( 'a', 5, ' ' );
// returns '    a'

str = lpad( 'beep', 10, 'b' );
// returns 'bbbbbbbeep'

str = lpad( 'boop', 12, 'beep' );
// returns 'beepbeepboop'

• An output string is not guaranteed to have a length of exactly len, but to have a length of at least len. To generate a padded string having a length equal to len

  var str = lpad( 'boop', 10, 'beep' ); // => length 12
  // returns 'beepbeepboop'
  
  str = str.substring( str.length-10 ); // => length 10
  // returns 'epbeepboop'

• This function differs from String.prototype.padStart in the following ways:

  • The function is not guaranteed to return a string having a length exactly equal to len (as explained above).
  • The function does not truncate pad (from the end) in order to ensure the returned string has length len.

  To replicate String.prototype.padStart truncation behavior

  var floorb = require( '@stdlib/math/base/special/floorb' );
  
  function padStart( str, len, pad ) {
      var n;
      if ( len <= str.length ) {
          return str;
      }
      n = floorb( len-str.length, 1, pad.length ) + str.length;
      return pad.substring( 0, len-n ) + lpad( str, n, pad );
  }
  
  var str = padStart( 'boop', 10, 'beep' );
  // returns 'bebeepboop'