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javascriptarrays
Maciej916
Maciej916

Reputation: 69

How to skip same values and get array length

I have my example array:

var person = [{
    firstName:"John",
    lastName:"Doe",
    age:46
},
{
    firstName:"Alexander",
    lastName:"Bru",
    age:46
},
{
    firstName:"Alex",
    lastName:"Bruce",
    age:26
}];

Simple person.length gives me the length of my array, but I need to merge values when the age is the same. So if two people have same age return 1 no 2. Sorry for my bad English, I can made a mistakes.

Upvotes: 3

Views: 278

Answers (4)

thgaskell
thgaskell

Reputation: 13236

If you are allowed to, you could add all the ages to a set and take its size.

const people = [{
  firstName: "John",
  lastName: "Doe",
  age: 46
}, {
  firstName: "Alexander",
  lastName: "Bru",
  age: 46
}, {
  firstName: "Alex",
  lastName: "Bruce",
  age: 26
}];

const ages = new Set(people.map(person => person.age));
console.log(ages.size)

Upvotes: 0

user663031
user663031

Reputation:

Filter the array down to only those elements for which a find on the array for the first element with the same age yields the element itself, then take the length of the result:

array.filter(o1 => o1 === array.find(o2 => o2.age === o1.age)).length

Another idea involves using a little function called uniqueCount, which counts the number of unique values in a (sorted) array:

function uniqueCount(a) {
  return a.reduce((cnt, elt, i) => a[i] === a[i-1] ? cnt : cnt + 1), 0);
}

Now you can create an array of all the ages, and do a count of its unique elements on it:

uniqueCount(array.map(e => e.age).sort(numeric))

Upvotes: 0

Pranav C Balan
Pranav C Balan

Reputation: 115232

Use Array#forEach method with an object reference for age.

var person = [{
  firstName: "John",
  lastName: "Doe",
  age: 46
}, {
  firstName: "Alexander",
  lastName: "Bru",
  age: 46
}, {
  firstName: "Alex",
  lastName: "Bruce",
  age: 26
}];
// object for storing reference to age
var obj = {},
  res = 0;
// iterate and count
person.forEach(function(v) {
  // check age already not defined
  if (!obj[v.age]) {
    // define the property
    obj[v.age] = true;
    // increment count
    res++;
  }
});

console.log(res);

Upvotes: 2

ryan
ryan

Reputation: 1084

you can use underscore or similar library that supports groupBy:

_.size(_.groupBy(person, "age"))

Upvotes: 2

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