var cashRegister = {? ? total:0,? ? add: function(itemCost){? ? ? ? this.total += itemCost;? ? },? ? scan: function(item,time) {? ? ? ? switch (item) {? ? ? ? case "eggs":?? ? ? ? for (var i = 0;i <= time - 1;i++) {this.add(0.98);}; break;? ? ? ? case "milk":?? ? ? ? for (var j = 0;j <= time - 1;j++) {this.add(1.23);}; break;? ? ? ? case "magazine":?? ? ? ? for (var k = 0;k <= time - 1;k++) {this.add(4.99);}; break;? ? ? ? case "chocolate":?? ? ? ? for (var l = 0;l <= time - 1;l++) {this.add(0.45);}; break;? ? ? ?// 上面的代碼錯在哪里，為什么不能正確實現（下面是可以實現功能的代碼）? ? ? ? // case "eggs": this.add(0.98 * time); break;? ? ? ? // case "milk": this.add(1.23 * time); break;? ? ? ? // case "magazine": this.add(4.99 * time); break;? ? ? ? // case "chocolate": this.add(0.45 * time); break; ? ?? ? ? ? }? ? }};// scan each item 4 timesvar myArr = ["eggs","milk","magazine","chocolate"];for ( var m = 0;m <= myArr.length - 1 ; m++ ) {? ? cashRegister.scan(myArr[m],4);};//Show the total billconsole.log('Your bill is '+cashRegister.total);