匿名函数和闭包

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function(){return 'dog';}     //匿名函数直接运行报语法错误,无法调用

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var box = function(){return 'dog';};     //可以
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box();

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(function(){     //(匿名函数)();
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return 'dog';
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})();     //等于上面的程序

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(function(age){
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return age;
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})(20);

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function box() {
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  return function () {     //闭包
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    return 'dog';
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  };
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}
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alert(box()());     //dog,执行普通函数里的匿名个函数,或者用下面的办法
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var b = box();     //同上
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alert(b());

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function box(){
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var age = 100;
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}
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alert(age);     //访问不到
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function box(){
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var age = 20;
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return function(){
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return age;
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}
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}
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alert(box()());     //这种方式可以

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//使用全局变量累加
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var age = 100;
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function box(){return age++;}
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alert(age);     //100
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box();
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alert(age);     //101
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//使用布局变量累加
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function box(){var age = 100; age++; return age;}
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alert(box());     //101
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alert(box());     //101
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//使用匿名函数实现局部变量驻留内存中
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function box(){
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  var age = 100;
8 collapsed lines
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  return function(){return ++age;};
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}
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var b = box();
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alert(b());     //101
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alert(b());     //102
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alert(age);     //101
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b = null;
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alert(b);

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function box() {
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  var arr = [];
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  for (var i = 0; i < 5; i++) {
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    arr[i] = function () {
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      return i;
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    };
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  }
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  return arr;
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}
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//alert(box());
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var b = box();
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for (var i = 0; i < 5; i++) {alert(b[i]);}