Creating an array of arrays without duplicates to add values-CodePudding

I have an array of objects with number values that I am trying to loop over to get a result of and ARRAY of ARRAYS. Ive found examples of using for loop where the output is an ARRAY of OBJECTS. But I am having trouble looping over and adding the number values to create an array for each month value with the second value being a total of all the values listed for that month.

var input = [
  {month: "Jan", value: 3},
  {month: "Jan", value: 3.5},
  {month: "Feb", value: 2.1},
  {month: "Mar", value: 6},
  {month: "Apr", value: 4.3},
  {month: "May", value: 5.5},
  {month: "Jun", value: 7},
  {month: "Jun", value: 9},
  {month: "Jul", value: 7},
  {month: "Jul", value: 9},
  {month: "Jul", value: 7},
  {month: "Aug", value: 9},
  {month: "Sep", value: 9},
  {month: "Sep", value: 9},
  {month: "Oct", value: 8},
  {month: "Oct", value: 5},
  {month: "Oct", value: 3},
  {month: "Nov", value: 12},
  {month: "Nov", value: 19.5},
];

var result = [];

for (var i = 0; i < input.length; i  ) {
  var data = input[i];
  var found = false;
  console.log(result[1][1], "help");
  for (var j = 0; j < result.length; j  ) {
    if (result[j].month === data.month) {
      found = true;

      result[j][1]  = data.value;
      break;
    }
  }
  if (!found) {
    result.push([data.month, data.value]);
  }
}

Currently returns an array of arrays but it is not adding the values instead it is making an array for each object.

My expected output would be:

[["Jan", 6.5],["Feb", 2.1],["Mar", 6],["Jun", 16]...etc]

CodePudding user response：

An alternate approach using month as keys in an Object.

var input = [
  { month: "Jan", value: 3 },
  { month: "Jan", value: 3.5 },
  { month: "Feb", value: 2.1 },
  { month: "Mar", value: 6 },
  { month: "Apr", value: 4.3 },
  { month: "May", value: 5.5 },
  { month: "Jun", value: 7 },
  { month: "Jun", value: 9 },
  { month: "Jul", value: 7 },
  { month: "Jul", value: 9 },
  { month: "Jul", value: 7 },
  { month: "Aug", value: 9 },
  { month: "Sep", value: 9 },
  { month: "Sep", value: 9 },
  { month: "Oct", value: 8 },
  { month: "Oct", value: 5 },
  { month: "Oct", value: 3 },
  { month: "Nov", value: 12 },
  { month: "Nov", value: 19.5 },
];

const totalMonthObj = {};
for (monthObj of input) {
  if (totalMonthObj[monthObj.month]) {
    totalMonthObj[monthObj.month].value  = monthObj.value;
  } else {
    totalMonthObj[monthObj.month] = monthObj;
  }
}
console.log(Object.values(totalMonthObj).map(({month,value})=>[month,value]));

CodePudding user response：

You can use array.reduce:

const result = input.reduce((r, item) => {
  const { month, value } = item;
  const existing = r.find((x) => x[0] === month);
  if (existing) {
    existing[1]  = value;
  } else {
    r.push([month, value]);
  }
  return r;
}, []);

Output:

console.log(JSON.stringify(result));

[["Jan",6.5],["Feb",2.1],["Mar",6],["Apr",4.3],["May",5.5],["Jun",16],["Jul",23],["Aug",9],["Sep",18],["Oct",16],["Nov",31.5]]

CodePudding user response：

just pass the months array to the function and it will return your expectation

function filterMonth(arr){


let data = [];

for (let index = 0; index < arr.length; index  ) {
    let findIndex = data.findIndex(item => item[0] === arr[index].month)
    if (findIndex === -1){
    data.push([arr[index].month,arr[index].value])
    }
}
return data

}

NOTE** this function will only work if the given array is just like yours

CodePudding user response：

Arrays don't have .month attributes associated with them. Look in your code below.

var input = [
  {month: "Jan", value: 3},
  {month: "Jan", value: 3.5},
  {month: "Feb", value: 2.1},
  {month: "Mar", value: 6},
  {month: "Apr", value: 4.3},
  {month: "May", value: 5.5},
  {month: "Jun", value: 7},
  {month: "Jun", value: 9},
  {month: "Jul", value: 7},
  {month: "Jul", value: 9},
  {month: "Jul", value: 7},
  {month: "Aug", value: 9},
  {month: "Sep", value: 9},
  {month: "Sep", value: 9},
  {month: "Oct", value: 8},
  {month: "Oct", value: 5},
  {month: "Oct", value: 3},
  {month: "Nov", value: 12},
  {month: "Nov", value: 19.5},
];

// your code with error correction

result = []

for (var i = 0; i < input.length; i  )
{
  var data = input[i]; // this is redundant but we can keep it
  var found = false;
  for (var j = 0; j < result.length; j  )
  {

    /* ----------------------------------------------------------
       ------------------------- HERE ------------------------
    ---------------------------------------------------------- */

    //if (result[j].month === data.month)
    // your if statement was never hit, because result[j] is an array
    // and doesn't have a month attribute, so it should return null,
    // thus never hitting your if statement
    if (result[j][0] === data.month)
    {
      found = true;
      result[j][1]  = data.value;
      break;
    }
  }
  if (!found) {
    result.push([data.month, data.value]);
  }
}

console.log(result)