JavaScript string_center，rjust，ljust

Posted 2021-05-19

String.prototype.ljust = function( width, padding ) {
	padding = padding || " ";
	padding = padding.substr( 0, 1 );
	if( this.length < width )
		return this + padding.repeat( width - this.length );
	else
		return this;
}
String.prototype.rjust = function( width, padding ) {
	padding = padding || " ";
	padding = padding.substr( 0, 1 );
	if( this.length < width )
		return padding.repeat( width - this.length ) + this;
	else
		return this;
}
String.prototype.center = function( width, padding ) {
	padding = padding || " ";
	padding = padding.substr( 0, 1 );
	if( this.length < width ) {
		var len		= width - this.length;
		var remain	= ( len % 2 == 0 ) ? "" : padding;
		var pads	= padding.repeat( parseInt( len / 2 ) );
		return pads + this + pads + remain;
	}
	else
		return this;
}

alert( "Ruby".center( 10 ) );      // "   Ruby   "
alert( "Ruby".rjust( 10 ) );       // "      Ruby"
alert( "Ruby".ljust( 10 ) );       // "Ruby      "
alert( "Ruby".center( 10, "+" ) ); // "+++Ruby+++"