How to remove an element from an array if it repeats the previous one?

Question

JavaScript

There is an array in which different values ​​\u200b\u200bare consecutive, how to remove the next value if it repeats the previous one?

Answer 1

Remove from existing array:

for (let i = arr.length; --i > 0; ) {
  if (arr[i] === arr[i - 1]) {
    arr.splice(i, 1);
  }
}

Assemble a new array:
arr.filter((n, i, a) => !i || a[i - 1] !== n)

Answer 2

reduce

Answer 3

const arr = [1, 2, 3, 4, 5, 5, 6, 7, 8, 5, 9, 10, 1, 2, 3];

const cleanArr = a =>
  a.reduce( (a, c) => !a.includes( c ) ? (a.push(c), a) : a, []);

console.log( cleanArr( arr ) );
// [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]