How would you count in the Fibonacci Sequence?
var fib = function(params) {
    var iterations = params;


Why are you copying params into iterations, rather than just naming your parameter iterations?

    var output = [0];


That's not really your output is it? Perhaps there is a better name?

    for(var i = 1, j = 1; j &lt; iterations; j++){
        //i is the fibonacci sequence
        //j counts iterations
        output.push(i);
        i = parseInt(output[j]) + parseInt(output[j-1]);


Output already contains ints. There is no reason to parseInt it. Why don't you directly push on the array rather then storing it in an int? Furthermore, you don't actually need an array, you only need the last two elements. 

    }
        console.log(output[iterations-1]);


Fix the indent here. 
    }

fib("4");


Why are you passing a string?