Answer 1

!function timer() {
    return !function () {
        var timeid = setTimeout(function () {
            console.log("hahaha...")
            clearTimeout(timeid)
            timer()
        }, 1000)
    }()
}()

hahaha...（6个时候）
[Done] exited with code=1 in 7.024 seconds

hahaha...(19个时候）
[Done] exited with code=1 in 19.326 seconds

（不过这个测试不够准确.......）

Answer 2

大佬 这个是不是写错了呢

Answer 3

var a = 10;
(function () {
    console.log(a); 
    a = 5;
    console.log(window.a);
    var a = 20;
    console.log(a); 
})();
//  ===
var a = 10;
(function () {
    var a;
    console.log(a); // undefined
    a = 5;
    console.log(window.a);  //  此时是window.a => 10
    a = 20;
    console.log(a); //  20
});