自执行匿名函数语法和普通函数语法对比

var eatFunction = function (what_to_eat) {
  var sentence = ‘I am going to eat a ‘ + what_to_eat;
  console.log( sentence );
};
eatFunction( ‘sandwich‘ );

// is the same as

(function (what_to_eat) {
  var sentence = ‘I am going to eat a ‘ + what_to_eat;
  console.log(sentence);
})(‘sandwich‘);

// is the same as

(function (what_to_eat) {
  var sentence = ‘I am going to eat a ‘ + what_to_eat;
  console.log(sentence);
}(‘sandwich‘)); 

// Three of them output ‘I am going to eat a sandwich‘

唯一的区别是，变量 eatFunction 被移除了，使用一对括号把函数定义包了起来。