Question

我有点迷失，我有一个json格式的数据集，时间戳和ID如下：

[{
  "date":"2016-11-18 19:20:42","id_pa":"7"
},{
  "date":"2016-11-18 19:04:55","id_pa":"5"
},{
  "date":"2016-11-19 20:53:42","id_pa":"7"
},{
  "date":"2016-11-19 20:53:43","id_pa":"7"
},{
  "date":"2016-11-19 20:53:43","id_pa":"7"
},{
  "date":"2016-11-20 20:49:42","id_pa":"7"
},{
  "date":"2016-11-20 20:50:45","id_pa":"7"
},{
  "date":"2016-11-20 20:50:46","id_pa":"7"
}]

我想构建一个每天显示日期和ID数量的json。新的Json会是这样的：

[{
  "date":"18-11-2016","num_pa":"2"
},{
  "date":"19-11-2016","num_pa":"1"
},{
  "date":"20-11-2016","num_pa":"1"
}]

我认为我必须使用 .map 格式化日期，以便显示dd-mm-yyyy，然后使用 .filter 删除重复项，最后删除< strong> .reduce 计算每个日期的不同ID。到目前为止，我只完成了.map程序，但我不确定如何进行后续步骤，我的解决方案是否是最佳解决方案。

这是我的一段代码：

SwapSvc
    .getUsage (vm.id_fi)
    .then((data)=>{
        //console.log(`lreceived data: `+ JSON.stringify(data) );
        vm.fdata = data.map((elem) => {
        //console.log(`date: ${elem.date}`);
        //console.log(`id_pa: ${elem.id_pa}`);
        var d = new Date (elem.date);
        return{
            date:d.getDate()+'-'+d.getMonth()+'-'+d.getFullYear()/*elem.date*/,
            id_pa:elem.id_pa
        }})
        var temp = [];
        vm.filteredData = vm.fdata.filter((elem, index) => {
            if(temp.indexOf(elem.date)<0){
                temp.push(elem);
                return true;
                }
            else return false;
        });
        console.log(`data after parsing and ordering: `+ JSON.stringify(vm.filteredData) ); 
        return data;
    })
    .catch((err)=>{
        //error
        console.log(`error, no response`);
        throw err;
    });

PS：我正在使用角度1.6和ES6。提前致谢 BRJ

Answer 1

您可以使用哈希表作为日期，并收集所有id_pa以便以后计算。

＆＃13;

var data = [{ date: "2016-11-18 19:20:42", id_pa: "7" }, { date: "2016-11-18 19:04:55", id_pa: "5" }, { date: "2016-11-19 20:53:42", id_pa: "7" }, { date: "2016-11-19 20:53:43", id_pa: "7" }, { date: "2016-11-19 20:53:43", id_pa: "7" }, { date: "2016-11-20 20:49:42", id_pa: "7" }, { date: "2016-11-20 20:50:45", id_pa: "7" }, { date: "2016-11-20 20:50:46", id_pa: "7" }],
    hash = Object.create(null),
    result;

data.forEach(function (a) {
    var date = a.date.slice(0, 10);
    hash[date] = hash[date] || Object.create(null);
    hash[date][a.id_pa] = true;
});
result = Object.keys(hash).map(date => ({ date, num_pa: Object.keys(hash[date]).length }));

console.log(result);

＆＃13;

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

＆＃13;

Answer 2

您可以将reduce链接到map调用，并使用ES6 findIndex方法查看当前对象是否存在于reduce函数创建的数组中

SwapSvc
    .getUsage (vm.id_fi)
    .then((data)=>{
        //console.log(`lreceived data: `+ JSON.stringify(data) );
        vm.fdata = data.map((elem) => {
        //console.log(`date: ${elem.date}`);
        //console.log(`id_pa: ${elem.id_pa}`);
        var d = new Date (elem.date);
        return{
            date:d.getDate()+'-'+d.getMonth()+'-'+d.getFullYear()/*elem.date*/,
            id_pa:elem.id_pa
        }}).reduce((p, c, i) => {
            var index = p.findIndex(x => x.date === c.date);
            if (index !== -1) p[index].num_pa++;
            else p.push({"date": c.date, "num_pa": 1})
            return p;
        }, [])

        console.log(`data after parsing and ordering: `+ JSON.stringify(vm.fData) ); 
        return data;
    })

格式化Json，删除重复项并在javascript中计算元素

2 个答案: