求解一道关于js的百度笔试题

Question

var name = "World";

(function () {

  if (typeof name === 'undefined') {

    var name = 'Jack';

    console.log('Goodbye' + name);

  } else {

    console.log('hello ' + name);

  }

})()

输出：GoodbyeJack

Answer 1

变量声明提升: 变量的声明会提升到当前作用域的顶部你的代码等于var name = "World";(function () {  var name //声明提升  if (typeof name === 'undefined') {    name = 'Jack';    console.log('Goodbye' + name);  } else {    console.log('hello ' + name);  }})()