The Problem

Given an array of numbers, return an array of unique values.

The Solution

There are a few ways to do this. One way is to use the includes method with an empty array. Check to see if an element is present in the array, if it is not, push it to the array. Return the array.

function unique(array) {
  // hold is empty object to hold results of test
  const hold = [];
  // iterate over array
  for (const element of array){
    // if hold does not include element push element to hold;
     !hold.includes(element) && hold.push(element); 
  }
    // return hold
    return hold;
}

unique([1,1,2,3,3,4,5]) // [ 1, 2, 3, 4, 5 ]
unique([1,1,1,1,1]) // [1]
unique([ 1, 2, 1, 3, 1, 4 ]) // [1,2,3,4]

Here is another solution using the new Set constructor.

const unique = array => [...new Set(array)];


unique([1,1,2,3,3,4,5]) // [ 1, 2, 3, 4, 5 ]
unique([1,1,1,1,1]) // [1]
unique([ 1, 2, 1, 3, 1, 4 ]) // [1,2,3,4]