phaser源码解析（二） Phaser.Utils类下pad方法

/**
*#填充字符串方法
* Javascript string pad http://www.webtoolkit.info/.
* pad = the string to pad it out with (defaults to a space) 
* dir = 1 (left), 2 (right), 3 (both)
* @method Phaser.Utils.pad 
* @param {string} str - The target string. ——#需要填充的字符 
* @param {number} len - The number of characters to be added. ——#填充的长度
* @param {string} pad - The string to pad it out with (defaults to a space).——#填充的字符
* @param {number} [dir=3] The direction dir = 1 (left), 2 (right), 3 (both).——#填充的位置（左、右、两边）
* @return {string} The padded string ——#填充好的字符
*/
pad: function (str, len, pad, dir) {

if (typeof(len) == "undefined") { var len = 0; }
if (typeof(pad) == "undefined") { var pad = ' '; }
if (typeof(dir) == "undefined") { var dir = 3; }

var padlen = 0;

if (len + 1 >= str.length)
{
switch (dir)
{
case 1:
str = Array(len + 1 - str.length).join(pad) + str;
break;

case 3:

// Math.ceil向上取整
var right = Math.ceil((padlen = len - str.length) / 2);
var left = padlen - right;
str = Array(left+1).join(pad) + str + Array(right+1).join(pad);
break;

default:
str = str + Array(len + 1 - str.length).join(pad);
break;
}
}

return str;

}