JavaScript ast:how to Convert switch to if statement in JavaScript?

hey guys!How to use ast convert code1 to code2？

I’ve been given a task that I have pretty much solved myself but there is some small correction that needs to be made and I need a help from someone to point me out of how to merge nodes!
My idea is to deal with ForStatement，find initialization params like ‘var t = 1’, then find the case, but I don’t have a good idea about how to merge nodes,please help me！thanks!
code1:

var a, b, c, d;
for (var t = 1; void 0 !== t;) {
    switch (t) {
        case 1:
            a = 4
            t = 2
            break;
        case 2:
            b = 0
            t = 3;
            break;
        case 3:
            if (c) {
                t = 4
            } else {
                t = 12;
            }
            break;
        case 4:
            t = 5;
            break;
        case 5:
            if (a > b) {
                t = 6;
            } else {
                t = 11;
            }
            break;
        case 6:
            t = 7;
            break;
        case 7:
            if (c > 0) {
                t = 8
            } else {
                t = 9
            }
            break;
        case 8:
            c = Math.floor(c / (b + 1));
            t = 7;
            break;
        case 9:
            t = 10;
            break;
        case 10:
            b++;
            t = 5;
            break;
        case 11:
            d = 'test1'
            break;
        case 12:
            d = 'test2'
            break;
    }
}

code2：

var a, b, c, d;
a = 4;
b = 0;
if (c) {
    while (a > b) {
        while (c > 0) {
            c = Math.floor(c / (b + 1));
        }
        b++;
    }
    d = 'test1'
} else {
    d = 'test2'
}