group array of objects by more than one parameter

Question

I'm trying to group array of objects by passing the key i want to group by as a parameter to a function i wrote, so for example if i have this array of 3 objects:

[{date: "2018-01-01", website: "example.com", revenue: 100},
 {date: "2018-01-01", website: "example2.com", revenue:200},
 {date: "2018-01-02", website: "example.com", revenue: 300}]

and i will pass them to my function:

    groupArr(arr, prop) {
        return arr.reduce(function (groups, item) {
            const val = item[prop];
            groups[val] = groups[val] || [];
            groups[val].push(item);
            return groups
        }, {})
    }

the result will be :{2018-01-01: Array(2), 2018-01-02: Array(1)}

but now i'm trying to figure out how can i change this function in a way that i can pass two parameters, for example date and website: groupArr(arr,["date","website"] so that my result will include group by two parameters, which in my case will end up like this:

{{[2018-01-01,"example.com"]: Array(1),[2018-01-01,"example2.com"]: Array(1), 2018-01-02: Array(1)}

i'm presenting the result key's as an array for convenience purposes, not sure if thats the right way to do so. any idea how can i achieve that? thanks

Nina Scholz · Accepted Answer · 2018-06-13 09:39:21Z

1

You could create a new key made of the values of the wanted properties.

function groupArr(arr, ...props) {
    return arr.reduce(function (groups, item) {
        const key = props.map(k => item[k]).join('|');
        groups[key] = groups[key] || [];
        groups[key].push(item);
        return groups;
    }, {});
}
var array = [{ date: "2018-01-01", website: "example.com", revenue: 100 },  {date: "2018-01-01", website: "example2.com", revenue: 200 }, { date: "2018-01-02", website: "example.com", revenue: 300 }, { date: "2018-01-01", website: "example.com", revenue: 340 }];
    grouped = groupArr(array, "date", "website");

console.log(grouped);

.as-console-wrapper { max-height: 100% !important; top: 0; }

edited Jun 13, 2018 at 9:39

answered Jun 13, 2018 at 9:33

Nina Scholz

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Eddie · Accepted Answer · 2018-06-13 09:35:30Z

1

You can do something like:

let arr = [{date: "2018-01-01",website: "example.com",revenue: 100},{date: "2018-01-01",website: "example2.com",revenue: 200},{date: "2018-01-02",website: "example.com",revenue: 300}];


function groupArr(arr, prop) {
  prop = Array.isArray(prop) ? prop : [prop];         //Make sure that prop is an array. Convert to array if not

  return arr.reduce(function(groups, item) {
    const val = prop.map(o => item[o]).join('-');     //Map and Concat all values of prop and use as key

    groups[val] = groups[val] || [];
    groups[val].push(item);
    return groups
  }, {})
}

//Will work if prop is array
let result = groupArr(arr, ["date", "website"]);
console.log(result);

//Will work if string
let result2 = groupArr(arr, "date");
console.log(result2);

answered Jun 13, 2018 at 9:35

Eddie

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1 Comment

yariv bar Over a year ago

Thanks, also a great solution which shows passing second parameter as array

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