Arrays and data processing in javascript

Question

So i have an array with objects which has the basic information such as:

var data = [{
 "id": 31737,
 "mobile": "123456",
 "name": "Jack",
 "time": "2019-12-15 13:52:43"
 },
 {
 "id": 31737,
 "mobile": "123456",
 "name": "Jack",
 "time": "2019-12-14 12:00:00"
 },
 {
 "id": 31737,
 "mobile": "123456",
 "name": "Jack",
 "time": "2019-12-14 09:15:05"
 },
 {
 "id": 88991,
 "mobile": "123456",
 "name": "Mike",
 "time": "2019-12-15 12:10:43"
 },
 {
 "id": 88991,
 "mobile": "123456",
 "name": "Mike",
 "time": "2019-12-15 10:52:43"
 },
 {
 "id": 88991,
 "mobile": "123456",
 "name": "Mike",
 "time": "2019-12-14 09:52:43"
 }
]

As you can see, the array stores the arrival time of each person. Same person has different arrival times, I need to make a function that returns new array, which stores each person's the latest arrival time(record) only. For returning the latest date, i found this answer answer, but can't really figure out how i should do in this situation, where similar id(or person) appears for couple times. How should i iterate so i can know that this timeis Mike's arrival time and not Jack's. Thank you.

• Niet the Dark Absol: Build an object that maps names to latest time. Loop through the list. If the name doesn't exist in the object or the time is more recent, add/update the entry in the object. Done.

Answer 1

took me a few minutes but I think I got it to work, if you click on the stackblitz at the bottom and check the console log you will see it gives the correct output.

var data = [{
 "id": 31737,
 "mobile": "123456",
 "name": "Jack",
 "time": "2019-12-15 13:52:43"
 },
 {
 "id": 31737,
 "mobile": "123456",
 "name": "Jack",
 "time": "2019-12-14 12:00:00"
 },
 {
 id: 31737,
 "mobile": "123456",
 "name": "Jack",
 "time": "2019-12-14 09:15:05"
 },
 {
 id: 88991,
 "mobile": "123456",
 "name": "Mike",
 "time": "2019-12-15 12:10:43"
 },
 {
 id: 88991,
 "mobile": "123456",
 "name": "Mike",
 "time": "2019-12-15 10:52:43"
 },
 {
 id: 88991,
 "mobile": "123456",
 "name": "Mike",
 "time": "2019-12-14 09:52:43"
 }
]
class timeCompare {
 constructor() {}
 payload = {}
 addEntry({
 id,
 time,
 mobile,
 name
 }) {
 if (!this[id]) {
 this.payload[id] = {
 'time': time,
 'name': name,
 'mobile': mobile
 }
 } else {
 var current = this.parseDate(this[id]['time'])
 var check = this.parseDate(time)
 if (check > current) {
 this.payload[id]['time'] = time
 }
 }
 }
 parseDate(dateString) {
 console.dir({
 'test': dateString
 })
 var d = dateString.substr(0, 10).split('-')
 var t = dateString.substr(11, 8)
 return Date.parse(`${d[1]}/${d[2]}/${d[0]} ${t}`)
 }
}
var control = new timeCompare()
data.forEach(_val => {
 control.addEntry(_val)
})
console.log(control)
var output = []
for (let OBJ in control.payload) {
 output.push({
 id: OBJ,
 ...control.payload[OBJ]
 })
}
console.log(output);

here is a working stackblitz

https://stackblitz.com/edit/typescript-3werja

Answer 2

Pass the data variable to this function to get the dates as a new array:

function getTime(dataset){
 var set = dataset.map(function(e){
 return e.time;
 });
 return set;
}

Then call the function as shown below:

var timeSet = getTime(data);

Answer 3

let output = data.reduce( (acc, item) => {
 let ids = acc.map(j => j.id);
 if(ids.includes(item.id)) {
 let existingItem = acc.filter( entry => entry.id === item.id);
 existingItem.time = Date.parse(item.time) > Date.parse(existingItem.time) ? 
 item.time : existingItem.toLocaleString;
 } else {
 acc.push(item);
 }
 return acc;
}, []);

Note the JSON provided is not well formed, I reformatted it and here is the full Code:

var data = [{
 "id": 31737,
 "mobile": "123456",
 "name": "Jack",
 "time": "2019-12-15 13:52:43"
 },
 {
 "id": 31737,
 "mobile": "123456",
 "name": "Jack",
 "time": "2019-12-14 12:00:00"
 },
 {
 "id": 31737,
 "mobile": "123456",
 "name": "Jack",
 "time": "2019-12-14 09:15:05"
 },
 {
 "id": 88991,
 "mobile": "123456",
 "name": "Mike",
 "time": "2019-12-15 12:10:43"
 },
 {
 "id": 88991,
 "mobile": "123456",
 "name": "Mike",
 "time": "2019-12-15 10:52:43"
 },
 {
 "id": 88991,
 "mobile": "123456",
 "name": "Mike",
 "time": "2019-12-14 09:52:43"
 }
];
let output = data.reduce((acc, item) => {
 let ids = acc.map(j => j.id);
 if (ids.includes(item.id)) {
 let existingItem = acc.filter(entry => entry.id === item.id);
 existingItem.time = Date.parse(item.time) > Date.parse(existingItem.time) ? item.time : existingItem.toLocaleString;
 return acc;
 } else {
 acc.push(item);
 return acc;
 }
}, []);
console.log(output);