How to remove duplicate elements in array in JS

Today I read Liao Xuefeng's JS tutorial and saw the usage of filter.

The method of using it to remove duplicate elements in Array is documented here.

Filter

filter is a common operation that filters out certain elements of Array and then returns the remaining elements.

Similar to map(), Array's filter() also receives a function. Unlike map(), filter() applies the passed function to each element in sequence, and then decides whether the return value is true or false to retain or discard the element.

Using filter, you can cleverly remove repeated elements of Array:

'use strict';
var
  r,
  arr = ['apple', 'strawberry', 'banana', 'pear', 'apple', 'orange', 'orange', 'strawberry'];
  r = (function (element, index, self) {
  return (element) === index;
});

Because indexOf in Array always returns the position where an element appears for the first time, the subsequent repeated element position is not equal to the position returned by indexOf, so it is filtered out by filter.

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