Question

假设我有一个看起来像这样的样本数组。

在这里的代码输出中它看起来像

[[2131, 2016-01-01, 1:00 PM, FA1], [2131, 2016-01-01, 2:00 PM, FA1], [2131, 2016-01-01, 3:00 PM, FA1], [2132, 2016-01-02, 4:00 PM, FA1].....]

我怎样才能看起来像这样？

我的意思是始终按日期对数据进行分组，并且只获取每个组的最后一组和第一组数据

我希望你得到我的观点TYSM

Answer 1

确定。根据您给出的输入，我构造了数组并根据需要获得输出。希望它有所帮助。

var inputarr = [ [ 2131, "2016-01-01", "1:00 PM", "FA1" ],
        [ 2131, "2016-01-01", "2:00 PM", "FA1" ],
        [ 2131, "2016-01-01", "3:00 PM", "FA1" ],
        [ 2132, "2016-01-02", "4:00 PM", "FA1" ],
        [ 2132, "2016-01-02", "5:00 PM", "FA1" ],
        [ 2132, "2016-01-02", "6:00 PM", "FA1" ],
        [ 2133, "2016-01-03", "7:00 PM", "FA1" ],
        [ 2133, "2016-01-03", "8:00 PM", "FA1" ],
        [ 2133, "2016-01-03", "9:00 PM", "FA1" ] ];

map = {};
for ( var element in inputarr) {
    if (!map[inputarr[element][1]]) {
        map[inputarr[element][1]] = [];
    }
    map[inputarr[element][1]].push(inputarr[element]);
}

output = [];

for ( var key in map) {
    output.push(map[key].shift());
    output.push(map[key].pop());
}

console.log(output);

输出：

[ [ 2131, '2016-01-01', '1:00 PM', 'FA1' ],
  [ 2131, '2016-01-01', '3:00 PM', 'FA1' ],
  [ 2132, '2016-01-02', '4:00 PM', 'FA1' ],
  [ 2132, '2016-01-02', '6:00 PM', 'FA1' ],
  [ 2133, '2016-01-03', '7:00 PM', 'FA1' ],
  [ 2133, '2016-01-03', '9:00 PM', 'FA1' ] ]

Answer 2

你可以做这样的事情

let arr = [[2131, "2016-01-01", "1:00 PM", "FA1"], [2131, "2016-01-01", "2:00 PM", "FA1"], [2131, "2016-01-01", "3:00 PM", "FA1"]
            , [2132, "2016-01-02", "4:00 PM", "FA1"], [2132, "2016-01-02", "5:00 PM", "FA1"], [2132, "2016-01-02", "6:00 PM", "FA1"]
            , [2133, "2016-01-03", "7:00 PM", "FA1"], [2133, "2016-01-03", "8:00 PM", "FA1"], [2133, "2016-01-03", "9:00 PM", "FA1"]]
let startMap = {};
let endMap = {};
let dateArray = [];
let resultArray = [];

for(let element of arr){
    console.log(element);
    if(startMap[element[1]] === undefined){
        startMap[element[1]] = element;
        dateArray.push(element[1]);
    }
    endMap[element[1]] = element;
}

for(let date of dateArray){
    resultArray.push(startMap[date]);
    resultArray.push(endMap[date]);
}
console.log(resultArray);

Answer 3

您可以使用此ES6脚本：

const data = [
    [2131, "2016-01-01", "1:00 PM", "FA1"], 
    [2131, "2016-01-01", "2:00 PM", "FA1"], 
    [2131, "2016-01-01", "3:00 PM", "FA1"],
    [2132, "2016-01-02", "4:00 PM", "FA1"],
    [2132, "2016-01-02", "5:00 PM", "FA1"],
    [2132, "2016-01-02", "6:00 PM", "FA1"], 
    [2133, "2016-01-03", "7:00 PM", "FA1"],
    [2133, "2016-01-03", "8:00 PM", "FA1"],
    [2133, "2016-01-03", "9:00 PM", "FA1"]
];

const result = [].concat(...data.reduce( (acc, a) =>
    acc.set(a[1], (acc.get(a[1]) || []).slice(0, 1).concat([a]))
, new Map).values());

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

解释

reduce与空Map一起用作起始值。然后使用日期作为键填充Map，并将匹配的原始值作为每个键的数组值。使用slice时，只有在添加新条目时才会保留此类数组的第一个条目。这样，每个数组中最多只能有2个值。

reduce返回最终Map后，会使用values从中提取值，并将其作为参数传播到concat，这将使其再次成为一个平面数组

对数组进行分组并获取每个组的最后一个和第一个数组

3 个答案:

解释