Adding Duplicated array values

Question

I Have an array [[Food , quantity]] with duplicated values and i want to add the quantities of the same food in the array but i can't seem to find a way to do that

I want to do this using JavaScript and the array looks like this:

[
  ["Burger", 5],
  ["Pizza", 10],
  ["Coke", 13],
  ["Burger", 7],
  ["Soda", 10],
  ["Pizza", 4],
  ["Burger", 12]
]

and i want the result to be like:

[
  ["Burger", 24],
  ["Pizza", 14],
  ["Coke", 13],
  ["Soda", 10]
]

And then I want to display the result on a table

Does the order of elements matter ? or it should be in some sorted manner ? — Code Maniac, Jun 06 '19 at 11:58
Possible duplicate of [Most efficient method to groupby on a array of objects](https://stackoverflow.com/questions/14446511/most-efficient-method-to-groupby-on-a-array-of-objects) — Alon Yampolski, Jun 06 '19 at 11:59

adiga · Answer 1 · 2019-06-06T12:13:52.357

You could use reduce to group each food. Create an accumulator with each food as key and the sum of quantity as value. If the key is already added, increment it. Else, add the key with quantity as value. Then use Object.entries() to get a 2D array of food - total quantity pairs

const input=[["Burger",5],["Pizza",10],["Coke",13],["Burger",7],["Soda",10],["Pizza",4],["Burger",12]]

const counter = input.reduce((acc, [food, value]) => {
  acc[food] = acc[food] + value || value;
  return acc;
}, {});

const ouptut = Object.entries(counter)

console.log(JSON.stringify(ouptut))

This is what the accumulator/ counter object will look like:

{
  "Burger": 24,
  "Pizza": 14,
  "Coke": 13,
  "Soda": 10
}

score 0 · Accepted Answer · answered Jun 06 '19 at 12:03

0

You can try something like -

const arr = [["Burger" , 5], ["Pizza" , 10], ["Coke" , 13], ["Burger" , 7], ["Soda" , 10], ["Pizza" , 4], ["Burger" , 12]];

let ans = [];
arr.map((x) => {
 const [name, qty] = x;
  const found = ans.find((y) => y[0] === name);
  if(found){
   found[1] = found[1] + qty;
  } else {
   ans.push(x);
  }
});
console.log(ans);

answered Jun 06 '19 at 12:03

Pranav Kale

629
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1

How does this work? What does `map` do, for example? – Andy Jun 06 '19 at 12:05

score 0 · Answer 3 · answered Jun 06 '19 at 12:05

You may try out like,

let array = [["Burger" , 5], ["Pizza" , 10], ["Coke" , 13], ["Burger" , 7], ["Soda" , 10], ["Pizza" , 4], ["Burger" , 12]];

let itemObj = {};

for(let item of array){
  if(itemObj.hasOwnProperty(item[0]))
    itemObj[item[0]] += item[1];
  else
    itemObj[item[0]] = item[1];
}

console.log(itemObj);

let newArray = Object.keys(itemObj).map(function(key) {
  return [key, itemObj[key]];
});

console.log(newArray);

Adding Duplicated array values

3 Answers3