JavaScript之PadLeft,PadRight

String.prototype.PadLeft = function(totalWidth, paddingChar)
{
if ( paddingChar != null )
{
return this.PadHelper(totalWidth, paddingChar, false);
} else {
return this.PadHelper(totalWidth, ' ', false);
}
}
String.prototype.PadRight = function(totalWidth, paddingChar)
{
if ( paddingChar != null )
{
return this.PadHelper(totalWidth, paddingChar, true);
} else {
return this.PadHelper(totalWidth, ' ', true);
}
}
String.prototype.PadHelper = function(totalWidth, paddingChar, isRightPadded)
{
if ( this.length < totalWidth)
{
var paddingString = new String();
for (i = 1; i <= (totalWidth - this.length); i++)
{
paddingString += paddingChar;
}
if ( isRightPadded )
{
return (this + paddingString);
} else {
return (paddingString + this);
}
} else {
return this;
}
}