Question

我需要用属于myData B 的那些元素和group匹配year中的元素的子元素group来子集答：

var myData = [{"year":1,"group":"A","value":0.1}, {"year":2,"group":"A","value":0.2}, {"year":3,"group":"A","value":0.2}, {"year":4,"group":"A","value":0.1}, {"year":5,"group":"A","value":0.1}, {"year":1,"group":"B","value":0.1}, {"year":2,"group":"B","value":0.2}, {"year":3,"group":"B","value":0.2}, {"year":4,"group":"B","value":0.2}, {"year":5,"group":"B","value":0.9}, {"year":6,"group":"B","value":0.1}] ;

我可以使用.filter()获得所需的输出：

mySubset = myData.filter((d) => {return d.group == "B" && d.year < 6;});

导致：

[{"year":1,"group":"B","value":0.1}, {"year":2,"group":"B","value":0.2}, {"year":3,"group":"B","value":0.2}, {"year":4,"group":"B","value":0.2}, {"year":5,"group":"B","value":0.9}];

但这不是理想的。我想要一个通用的通用解决方案，该解决方案不依赖于“手动”输入最大值（6）。另外，year可能不是序列（例如[2, 1, 4, 5]）。

基本上，障碍位于条件（d.year < 6）的第二部分。我需要与以下值匹配的东西：

let x = [] for(i = 0; i < myData.filter((d) => {return d.group == "A";}).length; i++){ x.push(myData[i].year); }

谢谢！

Answer 1

您首先可以创建一个Set，其中包含组A的所有年份，然后可以从数组中过滤出元素（如果该集合具有Year Year且该组是B，则可以添加）到结果）：

var myData = [{"year":1,"group":"A","value":0.1}, {"year":2,"group":"A","value":0.2}, {"year":3,"group":"A","value":0.2}, {"year":4,"group":"A","value":0.1}, {"year":5,"group":"A","value":0.1}, {"year":1,"group":"B","value":0.1}, {"year":2,"group":"B","value":0.2}, {"year":3,"group":"B","value":0.2}, {"year":4,"group":"B","value":0.2}, {"year":5,"group":"B","value":0.9}, {"year":6,"group":"B","value":0.1}];

let set = new Set(myData.filter(e=>e.group =="A").map(e=>e.year));

let result = myData.filter(e=> e.group =="B" && set.has(e.year));

console.log(result);

Answer 2

你在那儿；现在您已经有了“ A”组中所有年份的数组，您只需要检查“ B”组中的年份是否在该数组中。您可以为此使用.includes()。

mySubset = myData.filter((d) => {return d.group == "B" && x.includes(d.year);});

Answer 3

通过创建getSubset()函数，您可以将所需的组和年份作为参数传递（感谢@mhodges）

我还会过滤出yearGroups数组中所有可能为空的数组，以防年份不匹配任何内容

let myData = [
 {"year":1,"group":"A","value":0.1},
 {"year":2,"group":"A","value":0.2},
 {"year":3,"group":"A","value":0.2},
 {"year":4,"group":"A","value":0.1},
 {"year":5,"group":"A","value":0.1},
 {"year":1,"group":"B","value":0.1},
 {"year":2,"group":"B","value":0.2},
 {"year":3,"group":"B","value":0.2},
 {"year":4,"group":"B","value":0.2},
 {"year":5,"group":"B","value":0.9},
 {"year":6,"group":"B","value":0.1}
]


let getSubsets = (group = 'B', year = 6) => myData.filter(d => d.group == group && d.year < year)

console.log(getSubsets())

console.log(getSubsets('A', 4))

let yearGroups = [1,2,3,4,5].map(y => getSubsets('B', y)).filter(a => !!a.length)

console.log(yearGroups)

通过匹配值数组来子集javascript对象文字

3 个答案: