JS - array de duplication in the array object case

One 、 subject

Two 、 Code and effect

<script>
//  Method 1 ：
      var arr3 = ['c', 'a', 'z', 'a', 'x', 'a', 'x', 'c', 'b'];
      var newArr2 = [];
      // Traverse the old array , Compare it with the new array ,  The new array does not , Just save from the old array , If you have something, you won't save it .
      for (let i = 0; i < arr3.length; i++) {
        if (newArr2.indexOf(arr3[i]) === -1) { /* There are no original array elements in the new array , Just turn back -1*/
          newArr2[newArr2.length] = arr3[i]; /* Save the non-existent array in the new array */
        }
      }
      console.log(newArr2);


//  Method 2：
      var arr2 = ['c', 'a', 'z', 'a', 'x', 'a', 'x', 'c', 'b'];
      for (var i = arr2.length; i >= 0; i--) {  /*i In reverse order */
        for (let j = 0; j < arr2.length; j++) {   /*j positive sequence */
          /* When the elements are the same but the index numbers are different */
          if (arr2[i] === arr2[j] && arr2.indexOf(arr2[j]) !== arr2.lastIndexOf(arr2[i])) {
            var temp = arr2[i];
            arr2[i] = arr2[arr2.length - 1];
            arr2[arr2.length - 1] = temp;/*   Repeat the back one , Swap positions with the last element */
            arr2.pop();/* Delete the last element */
          }
        }
      }
      console.log(arr2);
</script>

3、 ... and 、 Ideas

Method 1 ：

 

Method 2 ：