compare array with object key and group in javascript

Question

i need to compare object key in array an need to group based on key value

const days = [
    {'name':'Mon','value':1}, 
    {'name':'Tue','value':5},
    {'name':'Wed','value':10},
    {'name':'Wed','value':30},
    {'name':'Fri','value':18},
    {'name':'Sat','value':80},
    {'name':'Sat','value':90},
    {'name':'Sun','value':20},
]

i need to group like this

const result [[1],[5], [10, 30], [18], [80, 90], [20]]

I am very new to javascript I not having any idea to do this. if its possible in lodash are es6 it will be fine.

you can achieve that with one reduce call which looks like this: days.reduce(fn, [[], [], [], [], [], [], []]) - try to figure out how fn should look like — pwolaq
– pwolaq, Commented Jan 22, 2018 at 12:22

Shubham Khatri · Accepted Answer · 2018-01-22 12:28:02Z

3

You could just loop over the object, and create a map of key to data and then just get the values using Object.values(newObj)

const days = [
    {'name':'Mon','value':1}, 
    {'name':'Tue','value':5},
    {'name':'Wed','value':10},
    {'name':'Wed','value':30},
    {'name':'Fri','value':18},
    {'name':'Sat','value':80},
    {'name':'Sat','value':90},
    {'name':'Sun','value':20},
]

let res = {}
days.forEach(obj => {
    res = {...res, [obj.name]: [...(res[obj.name] || []), obj.value]}
})

console.log(Object.values(res));

answered Jan 22, 2018 at 12:28

Shubham Khatri

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3 Comments

6round Over a year ago

thank for u reply i getting error on this line res = {...res, [obj.key]: [...(res[obj.key] || []), obj.value]}

6round Over a year ago

instead [obj.name] i am using [obj.key] can u tell anything wrong on it

Shubham Khatri Over a year ago

obj.key must exist for each of them and also it should be same for objects which have same name

Nina Scholz · Accepted Answer · 2018-01-22 12:31:39Z

2

You could take an object for same day and filter the result for getting only filled arrays.

var days = [{ name: 'Mon', value: 1 }, { name: 'Tue', value: 5 }, { name: 'Wed', value: 10 }, { name: 'Wed', value: 30 }, { name: 'Fri', value: 18 }, { name: 'Sat', value: 80 }, { name: 'Sat', value: 90 }, { name: 'Sun', value: 20 }], 
    slot = { Mon: 0, Tue: 1, Wed: 2, Thu: 3, Fri: 4, Sat: 5, Sun: 6 },
    result = [];

days.forEach(({ name, value }) => (result[slot[name]] = result[slot[name]] || []).push(value));

result = result.filter(Boolean);

console.log(result);

answered Jan 22, 2018 at 12:31

Nina Scholz

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1 Comment

Yury Tarabanko Over a year ago

The only correct answer so far. Since it doesn't rely on object keys ordering.

Nenad Vracar · Accepted Answer · 2018-01-22 12:37:21Z

0

With Lodash you can use groupBy and then map method to get desired result.

const days = [{"name":"Mon","value":1},{"name":"Tue","value":5},{"name":"Wed","value":10},{"name":"Wed","value":30},{"name":"Fri","value":18},{"name":"Sat","value":80},{"name":"Sat","value":90},{"name":"Sun","value":20}]

const result = _.chain(days)
  .groupBy('name')
  .values()
  .map(a => a.map(({value}) => value))
  
console.log(result)

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>

edited Jan 22, 2018 at 12:37

answered Jan 22, 2018 at 12:29

Nenad Vracar

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Comments

Ori Drori · Accepted Answer · 2018-01-22 13:22:45Z

0

Use Array#reduce to add the names and values to a map. Then get the Map's values iterator, and spread it back to an array:

const days = [{"name":"Mon","value":1},{"name":"Tue","value":5},{"name":"Wed","value":10},{"name":"Wed","value":30},{"name":"Fri","value":18},{"name":"Sat","value":80},{"name":"Sat","value":90},{"name":"Sun","value":20}]

const result = [...days.reduce((m, { name, value }) => {
  m.has(name) || m.set(name, []) // if the name is not in the map, add a new key with an empty array

  m.get(name).push(value) // get the array for the name, and push the value 

  return m 
}, new Map).values()] // convert the Map back to an array

console.log(result)

answered Jan 22, 2018 at 13:22

Ori Drori

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Comments

Hey24sheep · Accepted Answer · 2018-01-22 12:32:16Z

-1

You could use _.GroupBy , here is how you could do it.

 
const days = [
    { 'name': 'Mon', 'value': 1 },
    { 'name': 'Tue', 'value': 5 },
    { 'name': 'Wed', 'value': 10 },
    { 'name': 'Wed', 'value': 30 },
    { 'name': 'Fri', 'value': 18 },
    { 'name': 'Sat', 'value': 80 },
    { 'name': 'Sat', 'value': 90 },
    { 'name': 'Sun', 'value': 20 },
];

var t = _.groupBy(days, 'name');
result = [];
var s = Object.keys(t).forEach((i) => {
    var value = t[i];
    var temp = [];
    value.forEach((v) => {
        temp.push(v.value);
    });
    result.push(temp);
});

console.log(result);

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.js"></script>

edited Jan 22, 2018 at 12:32

answered Jan 22, 2018 at 12:24

Hey24sheep

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1 Comment

James Thorpe Over a year ago

The resulting object isn't anything remotely like what the OP asked for.

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