Find all subsequences of a string

JavaScript

function findSubSequences(str) {
    var len = str.length,
        output,
        counter = 0;
    for (var i = 1; i < Math.pow(2, len); i++) {
        output = '';
        for (var j = 0; j < len; j++) {
            if (i & (1 << j)) {
                output += str[j];
            }
        }
        
        console.log(output);
    }
}

findSubSequences('abc');