ES6: How to go through an array of object and change one of the items in there

Question

I'm trying to divide one item in array of objects by 1000 and return a new version with calculated value

0: {name: "Mon, 28", from: 10236, to: -0, time: "2019-01-28T18:51:04+01:00"}
1: {name: "Tue, 29", from: 10209, to: -0, time: "2019-01-29T18:51:03+01:00"}
2: {name: "Wed, 30", from: 12088, to: -0, time: "2019-01-30T18:51:01+01:00"}
3: {name: "Thu, 31", from: 10789, to: -0, time: "2019-01-31T18:50:59+01:00"}
4: {name: "Fri, 1", from: 11449, to: -0, time: "2019-02-01T18:50:56+01:00"}
5: {name: "Sat, 2", from: 13404, to: -0, time: "2019-02-02T18:50:48+01:00"}

const data2 = data.map(entry => {
        let rObj = {}
        rObj[entry.key] = entry.name
        rObj[entry.from] = entry.from / 1000
        rObj[entry.to] = entry.to
        rObj[entry.time] = entry.time
        return rObj
        // return entry.from
    })

I expect the result be like

0: {name: "Mon, 28", from: 10.236, to: -0, time: "2019-01-28T18:51:04+01:00"}
1: {name: "Tue, 29", from: 10.209, to: -0, time: "2019-01-29T18:51:03+01:00"}
2: {name: "Wed, 30", from: 12.088, to: -0, time: "2019-01-30T18:51:01+01:00"}
3: {name: "Thu, 31", from: 10.789, to: -0, time: "2019-01-31T18:50:59+01:00"}
4: {name: "Fri, 1", from: 11.449, to: -0, time: "2019-02-01T18:50:56+01:00"}
5: {name: "Sat, 2", from: 13.404, to: -0, time: "2019-02-02T18:50:48+01:00"}

any help would be appreciated.

Please post the code you've tried that isn't working, as well as the expected output. — CertainPerformance, Feb 02 '19 at 18:06
It's really not clear what you're asking. What does it mean to divide one item in this array by 10? Maybe you want to divide a property of every item in the array by 10? — Mark, Feb 02 '19 at 18:09
I need to divide the from element by 1000, and return the same array of object with the divided value — akano1, Feb 02 '19 at 18:12
Please post the actual array of objects so we can easily cut and paste it and work with it. Anyway this is a job for `map` or `forEach`, no ES6/ES7 necessary — Dexygen, Feb 02 '19 at 18:12
`const data2 = data.map(entry => ({...entry, from: (entry.from / 1000)}))` — Per Digesen, Feb 02 '19 at 18:13
Possible duplicate of [Update the attribute value of an object using the map function in ES6](https://stackoverflow.com/questions/49627157/update-the-attribute-value-of-an-object-using-the-map-function-in-es6) — adiga, Feb 02 '19 at 20:53

score 2 · Accepted Answer · answered Feb 02 '19 at 18:14

You can achieve this using map() method of arrays. If you using 0,1,2... as keys i would suggest you to use array instead. Below is example with array

const arr = [{name: "Mon, 28", from: 10236, to: -0, time: "2019-01-28T18:51:04+01:00"},
{name: "Tue, 29", from: 10.209, to: -0, time: "2019-01-29T18:51:03+01:00"},
{name: "Wed, 30", from: 12.088, to: -0, time: "2019-01-30T18:51:01+01:00"},
{name: "Thu, 31", from: 10.789, to: -0, time: "2019-01-31T18:50:59+01:00"},
{name: "Fri, 1", from: 11.449, to: -0, time: "2019-02-01T18:50:56+01:00"},
{name: "Sat, 2", from: 13.404, to: -0, time: "2019-02-02T18:50:48+01:00"}]

const newArr = arr.map(item => ({...item,from:item.from/1000}))
console.log(newArr)

score 0 · Answer 2 · answered Feb 02 '19 at 18:14

You can use map and destructing assignment

let obj = [{name: "Mon, 28", from: 10236, to: -0, time: "2019-01-28T18:51:04+01:00"},{name: "Tue, 29", from: 10209, to: -0, time: "2019-01-29T18:51:03+01:00"},{name: "Wed, 30", from: 12088, to: -0, time: "2019-01-30T18:51:01+01:00"},{name: "Thu, 31", from: 10789, to: -0, time: "2019-01-31T18:50:59+01:00"},{name: "Fri, 1", from: 11449, to: -0, time: "2019-02-01T18:50:56+01:00"},{name: "Sat, 2", from: 13404, to: -0, time: "2019-02-02T18:50:48+01:00"}]

const op = obj.map(e=>({...e, from: e.from/1000}))

console.log(op)

score 0 · Answer 3 · answered Feb 02 '19 at 18:16

You are almost there you just need to modify the from key and keep everything as it is. The destructing operator {...entry} will copy over all properties from the current element to the element which is going to be processed in the map function. Then I would only change the from key by dividing it by 1000.

const data =  [{name: "Mon, 28", from: 10236, to: -0, time: "2019-01-28T18:51:04+01:00"},{name: "Tue, 29", from: 10209, to: -0, time: "2019-01-29T18:51:03+01:00"},{name: "Wed, 30", from: 12088, to: -0, time: "2019-01-30T18:51:01+01:00"},{name: "Thu, 31", from: 10789, to: -0, time: "2019-01-31T18:50:59+01:00"},{name: "Fri, 1", from: 11449, to: -0, time: "2019-02-01T18:50:56+01:00"},{name: "Sat, 2", from: 13404, to: -0, time: "2019-02-02T18:50:48+01:00"}]
const data2 = data.map(entry => {
        const rObj = {...entry}
        rObj['from'] = entry['from']/1000;
        return rObj;          
    })
console.log(data2);

ES6: How to go through an array of object and change one of the items in there

3 Answers3