javascript - 估算 JavaScript 数组中的缺失值

Question

我有以下 JavaScript 代码，它使用 sql.js库与远程 SQL 数据库通信。

var xhr = new XMLHttpRequest();
xhr.open('GET', 'https://dl.dropboxusercontent.com/u/540963/test.sqlite', true);
xhr.responseType = 'arraybuffer';
var output = [];

xhr.onload = function(e) {
  var uInt8Array = new Uint8Array(this.response);
  var db = new SQL.Database(uInt8Array);
  var data = db.exec("SELECT year, weight FROM freq_data WHERE doi = 'D007266'");

  $.each(data[0].values, function(key, value) {
    output.push({'year': value[0], 'weight': value[1]});
  });
};
xhr.send();

输出存储在output数组中。例如，对于给定数组，数据如下:

{ year=1996,  weight=3}
{ year=1999,  weight=2}
{ year=2004,  weight=5}
{ year=2005,  weight=3}
{ year=2006,  weight=2}

数据存在一些差距；例如，没有 1997 年、1998 年、2000-2003 年的条目。我想知道如何估算数据以用 0 值填充缺失的年份，最终得到:

{ year=1996,  weight=3}
{ year=1997,  weight=0}
{ year=1998,  weight=0}
{ year=1999,  weight=2}
...
{ year=2006,  weight=2}

最合适的方法是什么？

Answer 1

假设数据将按年份排序，您可以像这样使用.reduce():

var data = [ { year: 1996,  weight: 3},
    { year: 1999,  weight: 2},
    { year: 2004,  weight: 5},
    { year: 2005,  weight: 3},
    { year: 2006,  weight: 2} ];
    
var final = data.reduce(function(prev, curr, index, arr) {
  prev.push(curr);
  if (index < arr.length - 1) {
    var nextYearInData = arr[index + 1].year;
    var yearToAdd = curr.year + 1;
    while (yearToAdd < nextYearInData) {
      prev.push({year: yearToAdd, weight: 0});
      yearToAdd++;
    }
  }
  return prev;
}, []);

console.log(final)