Display number of items from array of objects without duplicate

Question

I'm learning javascript and I have some problems. I would like to iterate an array of objects but with a few "options":

don't display duplicate items.
display the number of items.

expected result :

received 1

missed 2

dialed 3

I know how to iterate a array of objects and use .length to display the quantity of each item but I don't know iterate + display quantity + remove duplicates... Can you help me ?

const calls = [
  {
    type: "missed",
    date: "xx-xx-xx"
  },
  {
    type: "received",
    date: "xx-xx-xx"
  },
  {
    type: "dialed",
    date: "xx-xx-xx"
  },
  {
    type: "missed",
    date: "xx-xx-xx"
  },
  {
    type: "dialed",
    date: "xx-xx-xx"
  },
  {
    type: "dialed",
    date: "xx-xx-xx"
  }
];

Alex L · Accepted Answer · 2020-06-16 19:14:47Z

1

A good way to group items is with reduce (it’s also flexible, so if you add another type it works no problem):

const calls = [{
    type: "missed",
    date: "xx-xx-xx"
  },
  {
    type: "received",
    date: "xx-xx-xx"
  },
  {
    type: "dialed",
    date: "xx-xx-xx"
  },
  {
    type: "missed",
    date: "xx-xx-xx"
  },
  {
    type: "dialed",
    date: "xx-xx-xx"
  },
  {
    type: "dialed",
    date: "xx-xx-xx"
  }
];

const output = calls.reduce((aggObj, item) => {
    if(!aggObj[item.type]){
        aggObj[item.type] = 0
    }
    aggObj[item.type] += 1;
    return aggObj;
}, {});
//output as object:
console.log(output);

//output as array:
const outArr = Object.entries(output);
console.log(outArr);

//output as strings:
outArr.forEach(([k,v]) => console.log(k,v));

edited Jun 16, 2020 at 19:14

answered Jun 16, 2020 at 18:37

Alex L

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Comments

Alessio Cantarella · Accepted Answer · 2020-06-16 17:32:14Z

0

const calls = [{
    type: "missed",
    date: "xx-xx-xx"
  },
  {
    type: "received",
    date: "xx-xx-xx"
  },
  {
    type: "dialed",
    date: "xx-xx-xx"
  },
  {
    type: "missed",
    date: "xx-xx-xx"
  },
  {
    type: "dialed",
    date: "xx-xx-xx"
  },
  {
    type: "dialed",
    date: "xx-xx-xx"
  }
];
const types = ["missed", "received", "dialed"];
types.forEach(type => {
  console.log(type + ": " + calls.filter((calls) => calls.type === type).length);
});

answered Jun 16, 2020 at 17:32

Alessio Cantarella

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Comments

sonEtLumiere · Accepted Answer · 2020-06-16 18:23:37Z

0

i hope this helps

var newArr = calls.filter((x, index, self) =>
  index === self.findIndex((t) => (
    t.type === x.type && t.date === x.date)));

console.log(newArr);

answered Jun 16, 2020 at 18:23

sonEtLumiere

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