JSOutput.md

Javascript Output

Index of Topic

• What is the output?

What is the output

Hoisting

var b = 10;
(function b() {
  b = 20;
  console.log(b);
})();

声明提前：一个声明在函数体内都是可见的，函数声明优先于变量声明；在非匿名自执行函数中，函数变量为只读状态无法修改 Ref.: 第 33 题：下面的代码打印什么内容，为什么？

Hoisting and Assign Value

var a = 10;
(function () {
  console.log(a);
  a = 5;
  console.log(window.a);
  var a = 20;
  console.log(a);
})();

Ref.第 41 题：考察作用域的一道代码题

Radix

["1", "2", "3"].map(parseInt);

• ParseInt (string, radix)
• Radix is between 2-36

Read More

['10','10','10','10','10'].map(Number); // [10, 10, 10, 10, 10]

Ref. 第 2 题：['1', '2', '3'].map(parseInt) what & why ?

Hidden Type Conversion

var a = ?;
if(a == 1 && a == 2 && a == 3){
 	conso.log(1);
}

Ref.: 第 38 题：下面代码中 a 在什么情况下会打印 1？

Async

const promise = new Promise((resolve, reject) => {
  console.log(1);
  resolve(5);
  console.log(2);
}).then((val) => {
  console.log(val);
});

promise.then(() => {
  console.log(3);
});

console.log(4);

setTimeout(function () {
  console.log(6);
});

124536

Ref. 第 13 题：Promise 构造函数是同步执行还是异步执行，那么 then 方法呢？