javaScript中闭包的案例

 

以下是闭包的案例代码

//测试闭包
document.getElementById('button1').onclick = function() {
	var inputNodes = document.getElementsByTagName('input');
	var count = inputNodes.length;
	for (var index = 0; index < count; index++) {
		var inputNode = inputNodes[index];
		console.log(inputNode, inputNode.type);
		console.log('*******************');
		if (inputNode.type == 'text') {
			inputNode.onclick = (function(parameter) {
// 				alert('--' + index);
// 				alert('==' + parameter);
				return fn9(parameter);
			})(index);
		}
	}
};

//测试闭包
function fn9(param){
	var f = function fn10() {
		alert(param);
	}
	return f;
}

一些其他的案例代码

function fn1(){
	
	console.log(eval("{}")); //undefined
	console.log(eval('{}')); //undefined
	console.log(eval("({})")); //Object {  }
	console.log(eval('({})')); //Object {  }
	console.log(eval("(" + "{}" + ")")); //Object {  }
	console.log(eval('(' + '{}' + ')')); //Object {  }
// 	console.log(eval("(" + "{[]}" + ")")); //报错SyntaxError: expected expression, got ']'
// 	console.log(eval('(' + '{[]}' + ')')); //报错SyntaxError: expected expression, got ']'
	console.log(eval({})); //Object {  }
	console.log(eval({name:"jack"})); //Object { name: "jack" }
	console.log(eval('{name:"tom"}')); //tom
	console.log(eval("{name:'jerry'}")); //jerry
	var test = '{[], [], []}';
	console.log(eval(test)); //Array []
// 	console.log(eval('(' + test + ')')); //报错SyntaxError: expected expression, got ']'
// 	console.log(eval("(" + test + ")")); //报错SyntaxError: expected expression, got ']'

	var test2 = '{}';
	console.log(eval(test2)); //undefined
	console.log(eval('(' + test2 + ')')); //Object {  }
	console.log(eval("(" + test2 + ")")); //Object {  }
	
	var test6 = {};
	console.log(eval(test6)); //Object {  }
// 	console.log(eval('(' + test6 + ')')); //报错SyntaxError: missing ] after element list
// 	console.log(eval("(" + test6 + ")")); //报错SyntaxError: missing ] after element list
	
	var test3 = '[{}, {}]';
	console.log(eval(test3)); //Array [ {}, {} ]
	console.log(eval('(' + test3 + ')')); //Array [ {}, {} ]
	console.log(eval("(" + test3 + ")")); //Array [ {}, {} ]
	
	var test8 = {};
	//true false
	console.log(test8 instanceof Object, test8 instanceof Array);
	console.log(typeof test8); //object
	
	var test9 = [];
	//true true
	console.log(test9 instanceof Object, test9 instanceof Array);
	console.log(typeof test9); //object
	
}

fn1();

function fn2(){
	return 'hello';
}

var a = fn2();
console.log(a); //hello

function fn3(){
	return fn2();
}

var b = fn3();
console.log(b); //hello

function fn4(){
	var v = function fn5(){
		return '江西省赣州市于都县';
	}
	return v;
}

var result = fn4();
console.log(result); //function fn5()
console.log(result()); //江西省赣州市于都县

/*
打印出
******我是fn7()，我执行了******
江西于都县666
*/
console.log((function fn6(){
	var f = function fn7(){
		console.log('******我是fn7()，我执行了******');
		return '江西于都县666';
	}
	return f;
})()());


//测试闭包
document.getElementById('button1').onclick = function() {
	var inputNodes = document.getElementsByTagName('input');
	var count = inputNodes.length;
	for (var index = 0; index < count; index++) {
		var inputNode = inputNodes[index];
		console.log(inputNode, inputNode.type);
		console.log('*******************');
		if (inputNode.type == 'text') {
			inputNode.onclick = (function(parameter) {
// 				alert('--' + index);
// 				alert('==' + parameter);
				return fn9(parameter);
			})(index);
		}
	}
};

//测试闭包
function fn9(param){
	var f = function fn10() {
		alert(param);
	}
	return f;
}

function fn8() {
console.log('(' + null + ')'); //(null)
console.log(typeof ('(' + null + ')')); //string
console.log('(' + 666 + ')'); //(666)
// console.log('(' + abc + ')'); //ReferenceError: abc is not defined
console.log('(' + 'null' + ')'); //(null)
console.log(typeof ('(' + 'null' + ')')); //string
console.log(eval('(' + null + ')')); //null
console.log(eval('(null)')); //null
// console.log(eval('(' + '' + ')')); //SyntaxError: expected expression, got ')'
console.log(eval('(' + undefined + ')')); //undefined
// console.log(eval('(' + ')')); //SyntaxError: expected expression, got ')'
// console.log(eval('()')); //SyntaxError: expected expression, got ')'
}

fn8();

完！