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javascriptarraysforeachinclude

Simple solution remove duplicates in JS array. Must use push or pop and forEach

So, I'm still learning, so forgive the simple nature. But I'm trying to write a function called uniq(arr). If it worked it would return a new array without any duplicate values. It should not change the original array.

Here are two test calls which are currently not working. I'm not sure what the error implies > uniq([1, 2, 3]) Expected: [1, 2, 3] but got:

TypeError: undefined is not an object (evaluating 'copy.includes')

> uniq(['a', 'a', 'b']) Expected: ['a', 'b'] but got: TypeError: undefined is not an object (evaluating 'copy.includes')

function uniq(arr) {
  var copy;
  arr.forEach(function(item) {
    if (!copy.includes(item)) {
      push.copy(item);}})
  return copy
}
Solution

  • Set makes an array unique.

    const unique = (arr) => {
  return [... new Set(arr)];
}

console.log(unique([1, 2, 3, 3, 2, 5]))
// Output: [1, 2, 3, 5]