How to convert array of objects to array of arrays in javascript

Question

I have object of array of object. How to convert array of objects to array of arrays?

input = [
 {
 time: "2020-7",
 tasks: [
 {code: "p1", value: 1234},
 { code: "p2", value: 3445 },
 ]
 },
 {
 time: "2020-8",
 tasks: [
 { code: "p1", value: 3333 },
 { code: "p2", value: 4444 },
 ]
 }
]

I tried use forEach

let dataConvert=[], date=[],data=[];
input.forEach(x=>{
 return date = [...date, x.time]
})
console.log(date)
input.forEach(x=>{
 x.tasks.forEach(y=>{
 data = [...data,y.value]
 })
})
console.log(data);
dataConvert= [...dataConvert,date,data]

And get the results

dataConvert = [
 ["2020-7", "2020-8"],
 [1234, 3445, 3333, 4444]
]

I want the output looks like this:

output = [
 ["2020-7", "2020-8"],
 ["p1", 1234, 3333],
 ["p2", 3445, 4444],
]

Please help me.

• Harmandeep Singh Kalsi: Could you please show us some code you have tried so far?
• Yury Tarabanko: You need to show your code and describe what was the problem. Please read How to Ask and how to create minimal reproducible example.
• minhminh: @HarmandeepSinghKalsi I have edited the article

Answer 1

Try like below. Explanation is in comment.

let input = [
 {
 time: "2020-7",
 tasks: [
 {code: "p1", value: 1234},
 { code: "p2", value: 3445 },
 ]
 },
 {
 time: "2020-8",
 tasks: [
 { code: "p1", value: 3333 },
 { code: "p2", value: 4444 },
 ]
 }
];
// get array of time values.
let output = input.map(x => x.time);
// flatMap will create 1d array of tasks
// reduce will return object with key as code and value as an array of values for respective tasks.
let values = Object.values(input.flatMap(x => x.tasks).reduce((a, i) => {
 a[i.code] = a[i.code] || [i.code];
 a[i.code].push(i.value);
 return a;
}, {}));
// use spread operator to combine both values.
output = [output, ...values];
console.log(output);

• Krzysztof Kaczyński: @minhminh this is not the same structure because time elements are not inside an array. Please check my example

Answer 2

This should work for you:

const input = [{
 time: "2020-7",
 tasks: [{
 code: "p1",
 value: 1234
 },
 {
 code: "p2",
 value: 3445
 },
 ]
 },
 {
 time: "2020-8",
 tasks: [{
 code: "p1",
 value: 3333
 },
 {
 code: "p2",
 value: 4444
 },
 ]
 }
];
const time = [];
const tasks = new Map();
for (const elem of input) {
 time.push(elem.time);
 for (const task of elem.tasks) {
 if (tasks.has(task.code)) {
 tasks.get(task.code).push(task.value.toString())
 } else {
 tasks.set(task.code, [task.value.toString()]);
 }
 }
}
const result = [time];
for (const [key, value] of tasks.entries()) {
 result.push([key, ...value]);
}
console.log(result);