在JavaScript中对数组值进行分组
假设我们有一个包含一些年和周数据的对象数组，如下所示：
const arr = [
{year: 2017, week: 45},
{year: 2017, week: 46},
{year: 2017, week: 47},
{year: 2017, week: 48},
{year: 2017, week: 50},
{year: 2017, week: 52},
{year: 2018, week: 1},
{year: 2018, week: 2},
{year: 2018, week: 5}
];我们需要编写一个包含一个这样的数组的JavaScript函数。该函数应返回一个新数组，在该数组中，所有对“year”属性具有相同值的对象都被分组到一个单独的对象中。
因此，上述数组的输出对象应类似于-
[
{ 2017 : [{
week: 45,
week: 46,
week: 47,
week: 48,
week: 50,
week: 53
},
{ 2018 : [{
week: 1,
week: 2,
week: 5
}]
]示例
为此的代码将是-
const arr = [
{year: 2017, week: 45},
{year: 2017, week: 46},
{year: 2017, week: 47},
{year: 2017, week: 48},
{year: 2017, week: 50},
{year: 2017, week: 52},
{year: 2018, week: 1},
{year: 2018, week: 2},
{year: 2018, week: 5}
];
const groupByYear = arr => {
const res = [];
const map = {};
arr.forEach(item => {
const temp = {};
if (!map[item.year]) {
map[item.year] = [];
temp[item.year] = map[item.year];
res.push(temp);
};
map[item.year].push({ value: item.week });
});
return res;
};
console.log(JSON.stringify(groupByYear(arr), undefined, 4));输出结果
控制台中的输出-
[
{
"2017": [
{
"value": 45
},
{
"value": 46
},
{
"value": 47
},
{
"value": 48
},
{
"value": 50
},
{
"value": 52
}
]
},
{
"2018": [
{
"value": 1
},
{
"value": 2
},
{
"value": 5
}
]
}
]