// Define two arrays
var a = [100, 200];
var b = [[0, 3], [0, 4], [1, 5], [2, 5]];

// Define empty array for result
var result = [];

// Loop over 'b', each time adding next element in 'result'
for(var i in b) {
    result.push([a, b[i]]);
}

// In the end, 'result' contains the following array -
// [[[100, 200], [0, 3]], [[100, 200], [0, 4]], [[100, 200], [1, 5]], [[100, 200], [2, 5]]]