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Discussion on: Basic Javascript: Removing Duplicates from an Array

jamesthomson profile image
James Thomson

Don't forget reduce :)

const items = ['a','b','c','a','a','d','b','d','d','c'];

function removeDuplicates (arr){
  return arr.reduce((acc, curr) => acc.includes(curr) ? acc : [...acc, curr], []);
hilleer profile image
Daniel Hillmann

I was surprised this was not included :-)

jrdleto profile image

Can't figure out, what does [], in itterable condition

jamesthomson profile image
James Thomson

The reduce function uses and accumulator as part of its logic. The [] is the starting value (an empty array) of the accumulator.

Simplified, using the reduce function to produce a total based on an array of values, we could start the reduce loop with the value 0.

const arr = [1,2,3,4,5,6,7,8];

const newArr = arr.reduce((acc, cur) => acc + cur, 0) // 36

We could also start it with another value, perhaps as a running total.

More on reduce: