转换数据的逻辑

Question

I have an api that return me data in following format:

[
    {
        "_id": 1567362600000,
        "KIDate": "2019-09-02",
        "KITools": [
            {
                "data": 1,
                "tool": "A"
            },
            {
                "data": 2,
                "tool": "B"
            }
        ]
    },
    {
        "_id": 1567519839316,
        "KIDate": "2019-09-01",
        "KITools": [
            {
                "data": 2,
                "tool": "A"
            },
{
                "data": 1,
                "tool": "C"
            }
        ]
    },
    {
        "_id": 1567519839317,
        "KIDate": "2019-08-31",
        "KITools": [
            {
                "data": 0,
                "tool": "C"
            }
        ]
    },
  ]

I want to transform this data to get the following arrays:

Result 1 -  [“2019-09-02”,”2019-09-01”,”2019-08-31”]
Result 2 -  [ {name: ‘A’, data:[1, 2, 0] }, { name: 'B', data: [2, 0, 0] }, { name: 'C', data: [0, 1, 0]}]

Currently I am able to achieve this by using loops and per-defining variables with the tool name like following and looping the api data to push into this variable.

var result2 = [{ name: 'A', data: [] }, { name: 'B', data: [] }, { name: 'C', data: [] }];

But this is not the expected behavior, the tool names can change and I have to figure that out dynamically based on the data returned by the api. What is the best way to achieve this without looping like crazy.

Answer 1

You could use reduce method to get the result with array of dates and object of values for each tool.

 const data = [{"_id":1567362600000,"KIDate":"2019-09-02","KITools":[{"data":1,"tool":"A"},{"data":2,"tool":"B"}]},{"_id":1567519839316,"KIDate":"2019-09-01","KITools":[{"data":2,"tool":"A"},{"data":1,"tool":"C"}]},{"_id":1567519839317,"KIDate":"2019-08-31","KITools":[{"data":0,"tool":"C"}]}] const result = data.reduce((r, {KIDate, KITools}, i) => { r.dates.push(KIDate); KITools.forEach(({data: dt, tool}) => { if(!r.values[tool]) r.values[tool] = Array(data.length).fill(0); r.values[tool][i] = dt }) return r; }, {dates: [], values: {}}) console.log(result) 

Answer 2

You can use reduce and forEach with Set and Map

• Initialize accumulator as object with dates and data key, dates is a Set and data is Map
• For every element add the KIDate to dates key,
• Loop over KITools , check if that particular too exists in data Map if it exists update it's value by adding current values to id, if not set it's value as per current values

 let data = [{"_id": 1567362600000,"KIDate": "2019-09-02","KITools": [{"data": 1,"tool": "A"},{"data": 2,"tool": "B"}]},{"_id": 1567519839316,"KIDate": "2019-09-01","KITools": [{"data": 2,"tool": "A"},{"data": 1,"tool": "C"}]},{"_id": 1567519839317,"KIDate": "2019-08-31","KITools": [{"data": 0,"tool": "C"}]},] let final = data.reduce((op,{KIDate,KITools})=>{ op.dates.add(KIDate) KITools.forEach(({data,tool})=>{ if(op.data.has(data)){ op.data.get(data).data.push(tool) } else{ op.data.set(data, {name: data, data:[tool]}) } }) return op },{dates:new Set(),data: new Map()}) console.log([...final.dates.values()]) console.log([...final.data.values()]) 

Answer 3

The result1 array can be obtained via a direct .map() . To build the result2 array will require additional work - one approach would be to do so via .reduce() as detailed below:

 const data=[{"_id":1567362600000,"KIDate":"2019-09-02","KITools":[{"data":1,"tool":"A"},{"data":2,"tool":"B"}]},{"_id":1567519839316,"KIDate":"2019-09-01","KITools":[{"data":2,"tool":"A"},{"data":1,"tool":"C"}]},{"_id":1567519839317,"KIDate":"2019-08-31","KITools":[{"data":0,"tool":"C"}]}]; const result1 = data.map(item => item.KIDate); const result2 = data.reduce((result, item) => { item.KITools.forEach(kitool => { /* For current item, search for matching tool on name/tool fields */ let foundTool = result.find(i => i.name === kitool.tool); if (foundTool) { /* Add data to data sub array if match found */ foundTool.data.push(kitool.data); } else { /* Add new tool if no match found and init name and data array */ result.push({ name: kitool.tool, data: [kitool.data] }); } }); return result; }, []).map((item, i, arr) => { /* Second phase of processing here to pad the data arrays with 0 values if needed */ for (let i = item.data.length; i < arr.length; i++) { item.data.push(0); } return item; }); console.log('result1:', result1); console.log('result2:', result2);