How to accurately find the position of an array element

Title description

Find the position of the element item in the given array arr

Output description:

If item exists in the array, return the element The position in the array, otherwise -1 is returned
Input

indexOf([ 1, 2, 3, 4 ], 3)
Output

2

1 function indexOf(arr, item) {2     for(var i=0;i<arr.length;i++){3         if(arr[i]==item)4             return i;5         6     }7     return -1;8 }//此方法利用常见for循环从头遍历

1 function indexOf(arr, item) {

2 　return arr.indexOf(item);

// This method uses the indexOf() method of the JavaScript Array object. The indexOf() method can return the position where a specified string value first appears in the string. If the string is not found, it returns -1.

}

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