javascript - 使用 JavaScript 求和函数

Question

我正在尝试计算每月的门票数量。我拥有的数组:

[['tickets', 'month','year'], [1, "june",2016],[3, "june",2015],[1, "december",2015]]

我想要的结果:

[['year', 'june','december'], [2016,1,0],[2015,3,1]]

但我不知道如何用 JavaScript 来做到这一点。有什么帮助吗？谢谢，

Answer 1

一种可能的方法:我将日期分组到一个对象中，创建一个包含条目的唯一月份数组，然后将其处理为您想要的数组。

var inArray = [['tickets', 'month','year'], [1, "june",2016],[3, "june",2015],[1, "december",2015]]
var validMonths = {}

function dateReducer (acc, curr) {
  var year = curr[2]
  var month = curr[1]
  var num = curr[0]
  if (year === "year"){return acc}
  validMonths[month] = 0 // build unique array of valid months
  
  if (!acc[year]) {
    acc[year] = {}
    acc[year][month] = num
  } else {
    if (!acc[year][month]) {
      acc[year][month] = num
    } else {
      acc[year][month] += num
    }
  }
  return acc
}

var obj = inArray.reduce(dateReducer, {})
// This may be fine, depending on your needs
validMonths = Object.keys(validMonths)
var outArray = ["year"].concat(validMonths)

for (var year in obj) {
  if (obj.hasOwnProperty(year)){
    var subArray = [year]
    validMonths.forEach(v => {
      subArray.push(obj[year][v] || 0)
    })
    outArray.push(subArray)
  }
}

console.log(outArray)