duplicate.js

function duplicate(value, count) {
    var output = [];
    var duplicator = [value];
    var base = 1;
    while (count > 0) {
        if ((base & count) > 0) {
            output = output.concat(duplicator);
            count -= base;
        }

        duplicator = duplicator.concat(duplicator);
        base = base << 1; // this was just "base << 1" and didn't store the result, resulting in an infinite loop
    }
    return output;
}