// 全局的命名函数
  function add(x, y) {
    return x + y;
  }
  console.info(add(100, 200));  //300

    var func = function (x, y) {
      return x + y;
    }
    console.info(func(5, 2)); //7

    console.info(
      function (x, y) {
            return x + y;
          }(100, 200)  //立即调用
        );

    console.info(sum(10, 10));
    function sum(num1, num2) {
      return num1 + num2;
    }

    //console.info(sumFunc(10, 10));  //Uncaught TypeError: Property 'sumFunc' of object [object Object] is not a function 
    var sumFunc = function (num1, num2) {
      return num1 + num2;
    };
    console.info(sumFunc(10, 10));

 function func() {
 }
 console.info(func()); //undefined
 function func2() {
   return; //空的返回语句
 }
 console.info(func2()); //undefined

 var func = function (x, y) {
   var sum = x + y;
   return {
     value : sum
   }
 }

  var func = function (x, y) {
    var sum = x + y;
    return
    {
      value: sum
    };
  }
  console.info(func(5,5)); //undefined

  function add(x, y) {
    return x + y;
  }
  console.info(add(100, 200)); //300
  var other = add; //other和add引用同一函数对象
  console.info(other(300, 400)); //700
  console.info(typeof other);  //function
  console.info(add === other); //true

  function outerFunc(a, b) {
    function innerFunc(x) {
      return x * x;
    }
    return Math.sqrt(innerFunc(a) + innerFunc(b));
  }
  console.info(outerFunc(3, 4)); //5

 var globalStr = 'globalStr';
 function outerFunc2(argu) {
   var localVar = 100;
   function innerFunc2() {
     localVar++;
     console.info(argu + ":" + localVar + ":" + globalStr);
   }
   innerFunc2(); //hello:101:globalStr
 }
 outerFunc2("hello");

  function outerFunc(x) {
    var y = 100;
    return function innerFunc() {
      console.info(x + y);
    }
  }
  outerFunc(10)(); //110