var numberOfBits = 2;

function generateSequence(numberOfBits){
    var numberOfCombinations = Math.pow(2,numberOfBits),
    thisIteration,
    sequenceArray = [];

    for(var i=0; i< numberOfCombinations; i++){
        thisIteration = i.toString(2);
        // pad out the front
        while(thisIteration.length !== numberOfBits){
            thisIteration = "0" + thisIteration;
        }
        sequenceArray.push(thisIteration);
    }
    return sequenceArray.join(" ");
};

console.log(generateSequence(numberOfBits));