JavaScript闭包返回NaN吗？
[英]Javascript closures returns NaN?
问题描述
Trying to follow example in "Javascript: The Good Parts", creating a closure to be achieve hiding. 
尝试遵循“ Javascript：好的部分”中的示例，创建一个实现隐藏的闭包。 In the case a simple "account" object which has a balance that can't be changed directly: 如果是一个简单的“帐户”对象，其余额无法直接更改：
<head>
<script>
var myapp = {};
var account = function() {
var value = 0;
return {
"account_name": "",
deposit: function (amount) {
value = this.value + amount;
},
withdrawal: function (amount) {
value = this.value - amount;
},
balance: function( ) {
return value;
}
}
}();
myapp.account = account;
</script>
</head>
<body>
<script>
myapp.account.account_name = "Fred";
myapp.account.deposit(100);
myapp.account.withdrawal(25);
document.writeln("<p>Account name = " + myapp.account.account_name + "</p>");
document.writeln("<p>Balance = " + myapp.account.balance( ) + "</p>");
</script>
</body>
which yields the following: 结果如下：
Account name = Fred
Balance = NaN
Wny NaN? 不知道吗？
3 个解决方案
解决方案1
1 已采纳 2015-10-27 05:59:52
That's happening because you never set this.value . 发生这种情况是因为您从未设置过this.value 。 Basically, this can be fixed to just reference the closure'd variable value : 基本上，可以将其固定为仅引用闭包的变量value ：
var myapp = {};
var account = function() {
var value = 0;
return {
"account_name": "",
deposit: function (amount) {
value = value + amount;
},
withdrawal: function (amount) {
value = value - amount;
},
balance: function( ) {
return value;
}
}
}();
myapp.account = account;
myapp.account.account_name = "Fred";
myapp.account.deposit(100);
myapp.account.withdrawal(25);
$('p:nth-child(1)').text('Account name = ' + myapp.account.account_name);
$('p:nth-child(2)').text('Balance = ' + myapp.account.balance());
解决方案2
0 2015-10-27 06:16:48
Try it: i'm changed little bit your code.... this.value change into only value.. 尝试一下：我对您的代码进行了少许更改。
<head>
<script>
var myapp = {};
var account = function() {
var value = 0;
return {
"account_name": "",
deposit: function (amount) {
value = value + amount;
},
withdrawal: function (amount) {
value = value - amount;
},
balance: function( ) {
return value;
}
}
}();
myapp.account = account;
</script>
</head>
<body>
<script>
myapp.account.account_name = "Fred";
myapp.account.deposit(100);
myapp.account.withdrawal(25);
document.writeln("<p>Account name = " + myapp.account.account_name + "</p>");
document.writeln("<p>Balance = " + myapp.account.balance( ) + "</p>");
</script>
</body>
解决方案3
0 2015-10-27 08:09:59
when you assign account to myapp , the scope is missing, put var value outside the function 当您将account分配给myapp ， scope丢失，请将var value放在函数外部
var myapp = {};
var value = 0;
var account = (function(val){
return{
value: val,
"account_name": "",
deposit: function (amount) {
value = this.value + amount;
},
withdrawal: function (amount) {
value = this.value - amount;
},
balance: function( ) {
return value;
}
}
})(value);
console.log(account);
myapp.account = account;
myapp.account.account_name = "Fred";
myapp.account.deposit(100);
myapp.account.withdrawal(25);
console.log("<p>Account name = " + myapp.account.account_name + "</p>");
console.log("<p>Balance = " + myapp.account.balance( ) + "</p>");
声明:本站的技术帖子网页，遵循CC BY-SA 4.0协议，如果您需要转载，请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.