Trying to reduce an array of objects to a similar but summed up array of objects

Question

So I have an array of objects that looks like:

dataArray = [
    {Revenue: 5, Date: "2018-06-05T00:00:00", DateString: "6/5/2018"},
    {Revenue: 10, Date: "2018-06-05T00:00:00", DateString: "6/5/2018"},
    {Revenue: 5, Date: "2018-06-05T00:00:00", DateString: "6/5/2018"},
    {Revenue: 1, Date: "2018-06-13T00:00:00", DateString: "6/13/2018"},
    {Revenue: 4, Date: "2018-06-13T00:00:00", DateString: "6/13/2018"}
]

And what I need is to reduce that down to another array of objects that looks like:

reducedDataArray = [
    {Revenue: 20, Date: "2018-06-05T00:00:00", DateString: "6/5/2018"},
    {Revenue: 5, Date: "2018-06-13T00:00:00", DateString: "6/13/2018"}
]

Basically if the date is the same then the revenue needs to be summed up so that there aren't multiple instances of the same date. Unfortunately I am limited to our version of Typescript so I don't have all the cool ES6 goodies to help with this stuff. I've tried using things like reduce() but I think a combination of not knowing what the heck I'm doing and this being kind of weird has left me in a fog.

Any suggestions or insight would be greatly appreciated!

you don't need anything fancy to loop through and add totals by key (date) to a blank object, which you can then turn back into an array, deriving datestring from date; ES3 is plenty... — dandavis
– dandavis, Commented Jun 19, 2018 at 20:02

Titian Cernicova-Dragomir · Accepted Answer · 2018-06-19 20:22:00Z

3

You can use reduce to create an object with date keys and then convert the object back to an array.

let dataArray = [
    {Revenue: 5, Date: "2018-06-05T00:00:00", DateString: "6/5/2018"},
    {Revenue: 10, Date: "2018-06-05T00:00:00", DateString: "6/5/2018"},
    {Revenue: 5, Date: "2018-06-05T00:00:00", DateString: "6/5/2018"},
    {Revenue: 1, Date: "2018-06-13T00:00:00", DateString: "6/13/2018"},
    {Revenue: 4, Date: "2018-06-13T00:00:00", DateString: "6/13/2018"}
]
// We need to specify the type parameter explicitly, as it will not be inffered from initial value 
let valuesObj = dataArray.reduce<{ [date: string]: typeof dataArray[number] }>((p, v) => {
    const existing = p[v.Date];
    if (existing) {
        existing.Revenue += v.Revenue
    } else {
        p[v.Date] = Object.assign({}, v); //Create a copy so as to not change the original when we sum 
    }
    return p;
}, {});


// You can use Object.values(valuesObj) if available 
let values = Object.keys(valuesObj).map(k => valuesaObj[k]);

Playground link

edited Jun 19, 2018 at 20:22

answered Jun 19, 2018 at 20:10

Titian Cernicova-Dragomir

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2 Comments

Titian Cernicova-Dragomir Over a year ago

@prail and from my phone too :-P

awesome_treehouse Over a year ago

Thank you very much for taking the time to write this out. I really appreciate it.

Liang · Accepted Answer · 2018-06-19 23:20:21Z

1

Played with some loops and it works

dataArray = [
    {Revenue: 5, Date: "2018-06-05T00:00:00", DateString: "6/5/2018"},
    {Revenue: 10, Date: "2018-06-05T00:00:00", DateString: "6/5/2018"},
    {Revenue: 5, Date: "2018-06-05T00:00:00", DateString: "6/5/2018"},
    {Revenue: 1, Date: "2018-06-13T00:00:00", DateString: "6/13/2018"},
    {Revenue: 4, Date: "2018-06-13T00:00:00", DateString: "6/13/2018"}
];

const getUnique=array=>{
  return array.filter((value, index, self)=> { 
      return self.indexOf(value) === index;
  });
}

let date=[];
let output=[];

for(const v of dataArray) date.push(v.Date);
for(const v of getUnique(date)){

  let revenue=0,date=v,dateString;
  for(const x of dataArray){
    if(x.Date==v) revenue+=x.Revenue;
    dateString=x.DateString;
  }

  output.push({
    Revenue:revenue,
    Date:v,
    DateString:dateString
  });

}

console.log(output);

jsfiddle link

edited Jun 19, 2018 at 23:20

answered Jun 19, 2018 at 23:14

Liang

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1 Comment

awesome_treehouse Over a year ago

Thank you so much! I'm marking this as the answer because it follows a similar pattern to other code I'm working with.

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