Javascript indexOf method with multiple values

Question

I have an array wich contains multiple same values

[\"test234\", \"test9495\", \"test234\", \"test93992\", \"test234\"]
         


        

Answer 1

You can use the fromIndex of Array#indexOf.

fromIndex

The index to start the search at. If the index is greater than or equal to the array's length, -1 is returned, which means the array will not be searched. If the provided index value is a negative number, it is taken as the offset from the end of the array. Note: if the provided index is negative, the array is still searched from front to back. If the calculated index is less than 0, then the whole array will be searched. Default: 0 (entire array is searched).

~ is a bitwise not operator.

It is perfect for use with indexOf(), because indexOf returns if found the index 0 ... n and if not -1:

value  ~value   boolean
-1  =>   0  =>  false
 0  =>  -1  =>  true
 1  =>  -2  =>  true
 2  =>  -3  =>  true
 and so on 

var array = ["test234", "test9495", "test234", "test93992", "test234"],
    result = [],
    pos = array.indexOf('test234');

while (~pos) {
    result.push(pos);
    pos = array.indexOf('test234', pos + 1); // use old position incremented
} //                               ^^^^^^^

document.write('
 ' + JSON.stringify(result, 0, 4) + '
');