JavaScript 使用 splice() 对数组进行排序，结果为 NaN

Question

我正在尝试根据月份对数组进行排序。我的示例输入:

var result = [{date: '2017/01/23', total: 364.59999999999997},
{date: '2017/04/07', total: 32.7},
{date: '2017/04/25', total: 42.99999999999999},
{date: '2017/07/01', total: 15.37},
{date: '2017/12/02', total: 33.980000000000004},
{date: '2017/03/26', total: 50.6},
{date: '2017/03/13', total: 65.1},
{date: '2017/10/13', total: 337.5},
{date: '2017/07/09', total: 50.2},
{date: '2017/11/02', total: 75}];

我想做的是首先提取月份，然后如果它们来自同一个月，我想总结总数。

var priceData = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0];
for(var i = 0; i < result.length; i++){

        var str = result[i].date;
        var month = str.substr(5, 2);

        if(month == '01'){ monthIndex = 0;}
        else if(month == '02'){ monthIndex = 1;}
        else if(month == '03'){ monthIndex = 2;}
        else if(month == '04'){ monthIndex = 3;}
        else if(month == '05'){ monthIndex = 4;}
        else if(month == '06'){ monthIndex = 5;}
        else if(month == '07'){ monthIndex = 6;}
        else if(month == '08'){ monthIndex = 7;}
        else if(month == '09'){ monthIndex = 8;}
        else if(month == '10'){ monthIndex = 9;}
        else if(month == '11'){ monthIndex = 10;}
        else if(month == '12'){ monthIndex = 11;}

        if(priceData[monthIndex] == 0){
            priceData.splice(monthIndex, 0, result[i].total);
        }else{
            var amount = priceData[monthIndex];
            var finalizedAmount = amount + result[i].total;
            priceData.splice(monthIndex, amount, finalizedAmount);
        }

        console.log('date ' + result[i].date + ' ' + result[i].total);
    }

首先，我检查priceData的索引是否为0。如果为0，我只需使用splice()替换它。如果没有，我得到以前的金额，然后与新的金额相加，然后替换它。但是，通过上面的代码，我得到的输出如下:

364.59999999999997
0
115.69999999999999
NaN
NaN
NaN

Answer 1

我认为如果将日期字符串解析为 native 日期对象，可以简化代码。您可以使用 getMonth将返回月份的 0 到 11 之间的整数。

另外，我用的是ES6 Array.fill()函数，因为现在是 2017 年，我们不需要循环用零填充数组:)

以下是我对问题的解决方案:

const result = [
  {date: '2017/01/23', total: 364.59999999999997},
  {date: '2017/04/07', total: 32.7},
  {date: '2017/04/25', total: 42.99999999999999},
  {date: '2017/07/01', total: 15.37},
  {date: '2017/12/02', total: 33.980000000000004},
  {date: '2017/03/26', total: 50.6},
  {date: '2017/03/13', total: 65.1},
  {date: '2017/10/13', total: 337.5},
  {date: '2017/07/09', total: 50.2},
  {date: '2017/11/02', total: 75}
];


const priceData = new Array(12).fill(0);

result.forEach(o => {
  const monthIndex = new Date(o.date).getMonth();
  priceData[monthIndex] += o.total;
});

console.log(priceData);