以下 CoffeeScript：greet = -> "This is an example of a function"編譯時(shí)生成以下 JavaScript 代碼：(function() {  var greet;    greet = function() {    return "This is an example of a function";  };}).call(this);我的問題是，為什么 JavaScript 不創(chuàng)建像這樣的單個(gè)函數(shù)：(var greet = function() {    return "This is an example of a function"};}).call(this);