// js quiz
// you have
function add() { return ["a","b"]; }
var tt = [1,2,3,4];
// you want
// [1,'a','b',2,3,4]
// modify tt using splice. How?
// My Solution:
tt=tt.splice(0,4,tt.splice(0,1,add()[1]));
tt=tt.splice(0,5,tt.splice(0,0,add()[0]));
tt=tt.splice(0,6,tt.splice(0,0,1));
// Show result:
document.getElementById("js_quiz_result").innerHTML = tt;
<div id ="js_quiz_result"></div>