function BookStrategy() {
 this.calcPrice = function( price ) {
 console.log("未打折 = " + price);
 }
}
function BookCalc9Strategy() {
 this.calcPrice = function( price ) {
 console.log("原價是："+ price +";打9折后：" + (price * 0.9));
 }
}
function BookCalc8Strategy() {
 this.calcPrice = function( price ) {
 console.log("原價是："+ price +";打8折后：" + (price * 0.8));
 }
}
function BookCalc7Strategy() {
 this.calcPrice = function( price ) {
 console.log("原價是："+ price +";打7折后：" + (price * 0.7));
 }
}
function PriceCalc( _strategy ) {
 this.strategy = _strategy;
 this.getPrice = function( price ) {
 return this.strategy.calcPrice( price );
 }
}
function Client() {
 var price = 100;
 var priceCalc = null;
 if ( 199 <= price && price < 399 ) {
 priceCalc = new PriceCalc(new BookCalc9Strategy());
 } else if ( 399 <= price && price < 599 ) {
 priceCalc = new PriceCalc(new BookCalc8Strategy());
 } else if ( 599 <= price ) {
 priceCalc = new PriceCalc(new BookCalc7Strategy());
 } else {
 priceCalc = new PriceCalc(new BookStrategy());
 }
 priceCalc.getPrice(price);
}
Client();