CODEWITHSUNDEEP
angulartypescript
Martin
Martin

Reputation: 121

Aggregate values and group by date in angular

I have an array of dates and a field with a number value. Now I am trying to use the reduce function to sort this out, I have googled a lot but I just cant find a solution.

The array i want to aggregate looks like this.

     test = [
    {
      xUsed: 10,
      date: "2021-01-01"

    },
    {
      xUsed: 10,
      date: "2021-01-01"

    },
    {
      xUsed: 3,
      date: "2021-01-02"

    }
  ];

The result i want is this.

result [ 
 { xUsed: 20,
   date: "2021-01-01 },
 { xUsed: 3,
   date: "2021-01-02 }
]

This is the code I am trying to use

   let res = this.test.reduce((acc, val ) => {
      acc[val.date] + +val.xUsed;
      return acc;
    },[]);

But i get a typescript error 7015, Element implicitly has an 'any' type because index expression is not of type 'number' on acc[val.date]

Any idea?

Upvotes: 1

Views: 719

Answers (1)

Eliseo
Eliseo

Reputation: 57929

A reduce it's easy. Take account you can use complex instructions

  result=this.test.reduce((acc:any, val:any ) => {
    //search in acc array if there're an element with the same "date"
    const element=acc.find(x=>x.date==val.date)
    if (!element)       //if not exist
        acc.push(val)   //add the val to acc
    else                //if exist
       element.xUsed+=val.xUsed   //simple increment the xUsed property
    return acc;
  },[]);

Imagine reduce as a forEach. You're iterating and each iteration the "val" is one element of the array. It's like

const acc=[];            //<--this is the "initial value" (the last argument of reduce)
this.test.forEach(val=>{
   const element=acc.find(x=>x.date==val.date)
   if (!element)
      acc.push(val)
   else
      element.xUsed+=val.xUsed
})
result=acc

Upvotes: 2

Related Questions