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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('<pre> ' + JSON.stringify(result, 0, 4) + '</pre>');