适用于json中的值折扣javascript

我有一个应用程序需要购买3本书（3本书：wiz [0]，lorax [1]和民主人士[2]）。这三本书的价格都是24.95美元，但两本书的价格是44.90美元（合计--5美元），三本书的价格是59.85美元（合计--10美元）。但是第4本或+书应该打折到19.95美元，没有进一步的折扣。我困在我的第三个函数“__totalWithDiscounts（）”。有没有人有任何想法如何做到这一点？我觉得它超级简单，但我不知道该怎么做。适用于json中的值折扣javascript

var cartJSON = [{'id':'wiz','count':0}, 
      {'id':'gorax','count':0}, 
      {'id':'democrat','count':0}] 

function __updateTheTotal(item,quantity){ 
    // find book being updated and change the count to the passed quantity 
for (var i=0; i<cartJSON.length; i++) { 
    if (cartJSON[i].id == item) { 
    cartJSON[i].count = quantity; 
    break; 
    } 
} 
__totalWithDiscounts(); 
} 

function __totalWithDiscounts(){ 
// this function will get the new json data generated by the inputs and apply discounts based on the amount 
var discount_offTwoBooks = Number(5); 
var discount_offThreeBooks = Number(10); 
var priceOfEachBook_default = Number(24.95); 
var priceOfEachBook_afterCountIs4 = Number(19.95); 
var totalOf_wiz = Number(cartJSON[0].count); 
var totalOf_gorax = Number(cartJSON[1].count); 
var totalOf_democrat = Number(cartJSON[2].count); 
var totalOf_all = +totalOf_wiz +totalOf_gorax +totalOf_democrat; 
console.log('total books: '+totalOf_all); 
}

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2016-04-26 chemi

我会这样做。没有经过测试，但很确定它会工作：

function __totalWithDiscounts(){ 
    // this function will get the new json data generated by the inputs and apply discounts based on the amount 
    var discount_offTwoBooks = Number(5); 
    var discount_offThreeBooks = Number(10); 
    var priceOfEachBook_default = Number(24.95); 
    var priceOfEachBook_afterCountIs4 = Number(19.95); 
    var totalOf_wiz = Number(cartJSON[0].count); 
    var totalOf_gorax = Number(cartJSON[1].count); 
    var totalOf_democrat = Number(cartJSON[2].count); 
    var totalOf_all = 0+totalOf_wiz +totalOf_gorax +totalOf_democrat; 
    console.log('total books: '+totalOf_all); 

    var priceOfAll = 0; 
    if(totalOf_all >=4) priceOfAll = totalOf_all * priceOfEachBook_afterCountIs4; 
    else if(totalOf_all == 3) priceOfAll = priceOfEachBook_default * 3 - discount_offThreeBooks; 
    else if(totalOf_all == 2) priceOfAll = priceOfEachBook_default * 2 - discount_offTwoBooks; 
    else priceOfAll = priceOfEachBook_default * 1; 
    }

一点建议：使用更好的变量名称。这是一个简单的分支逻辑构造。并不难把握：https://en.wikipedia.org/wiki/Conditional_(computer_programming)

来源

2016-04-26 23:04:07

这里是一个可以解决的的jsfiddle：https://jsfiddle.net/6p1n1tta/3/

var totalOf_all = totalOf_wiz + totalOf_gorax + totalOf_democrat; 
var discount = 0; 
    switch (totalOf_all) { 
    case 1: { 
     discount = 0; 
     break; 
    } 
    case 2: { 
     discount = discount_offTwoBooks; 
     break; 
    } 
    case 3: { 
     discount = discount_offThreeBooks; 
     break; 
    } 
    default: { 
     discount = priceOfEachBook_afterCountIs4; 
     break; 
    } 
    } 
var totalPrice = (totalOf_all * priceOfEachBook_default) - discount; 

console.log('total books: ' + totalOf_all + '\n' + 'total price: ' + totalPrice);

而且，在你__updateTheTotal功能，它应该是cartJSON[i].count += quantity;。在进行更改之前，计数无法正确更新。

来源

2016-04-26 23:12:30

适用于json中的值折扣javascript

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