详解JavaScript作用域 闭包

function foo(){
	var a = 2;
	function bar(){
		console.log(a);
	}
	return bar;
}
var baz = foo();
bzz(); //2

function foo(){
	var a = 2;
	function baz(){
		console.log(a);
	}
	bar(baz);
}

function bar(fn){
	fn();	// 这就是闭包
}

function wait(message){
	setTimeout( function timer(){
		console.log(message);
	},1000);
}
wait("Hello,ligang");

function setupBot(name, selector){
	$(selector).click(function activator(){
		console.log("Activating: "+ name);
	});
}
setupBot("Closure Bot 1", "#bot_1");
setupBot("Closure Bot 2", "#bot_2");

for(var i=1; i<=5; i++){
	setTimeout(function timer(){
		console.log(i);
	}, i*1000);
}
// 期望：每秒一次的频率输出1~5
// 结果：每秒一次的频率输出五次6

for(var i=0; i<=5; i++){
	(function(j){
		setTimeout(function timer(){
			console.log(j);
		}, j*1000 );
	})(i);
}
// 结果：每秒一次的频率输出1~5

for(var i=0; i<=5; i++){
	let j = i;
	setTimeout(function timer(){
		console.log(j);
	}, j*1000 );
}
// 结果：每秒一次的频率输出1~5
for(let i=0; i<=5; i++){
	setTimeout(function timer(){
		console.log(i);
	}, i*1000 );
}
// 结果：每秒一次的频率输出五次6

function CoolMoudle(){
	var something = "cool";
	var doSomething = function(){
		console.log(something);
	}
	return{
		doSomething: doSomething
	};
}
var foo = CoolMoudle();	//如果不执行外部函数CoolMoudle()，内部作用域和闭包都无法创建
foo.doSomething();	//cool

var foo = (function CoolModule(id){
	function change(){
		// 修改公共API
		publicAPI.identify = identify2;
	}
	function identify1(){
		console.log(id);
	}
	function identify2(){
		console.log(id.toUpperCase());
	}
	var publicAPI = {
		change: change,
		identify: identify1
	};
	return publicAPI;
})("foo module");
foo.identify();	//foo module
foo.change();
foo.identify(); //FOO MODULE