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问题描述
(function()
{
//codehere
}
)();
这种语法有什么特别之处? 什么是()();暗示?
推荐答案
创建一个匿名函数，闭合和全部，最终()告诉它执行自身.
基本上与:
function name (){...}
name();
因此，基本上，此代码没有什么特别的，它只是创建方法并调用它而无需命名的"快捷方式".
这也意味着该函数是一个关闭的功能，或者是对象上的内部函数，并且当您需要闭合功能时最有用.
其他推荐答案
这是一个匿名函数.
目的是创建一个新的范围，局部变量不会流血.例如:
var test = 1;
(function() {
var test = 2;
})();
test == 1 // true
关于此语法的一个重要说明是，如果您还没有，您应该养成用半彩色终止陈述的习惯.这是因为JavaScript允许在调用函数名称及其括号之间的行馈电.
下面的摘要将导致错误:
var aVariable = 1
var myVariable = aVariable
(function() {/*...*/})()
这是实际在做的:
var aVariable = 1;
var myVariable = aVariable(function() {/*...*/})
myVariable();
创建新块范围的另一种方法是使用以下语法:
new function() {/*...*/}
区别在于，以前的技术不会影响关键字" this"指向的位置，而第二个则不会影响
.JavaScript 1.8还具有完成同一件事的Let语句，但不用说，大多数浏览器不支持它.
其他推荐答案
这是一个自我执行的匿名函数.末尾的()实际上是在调用函数.
问题描述
(function()
{
//codehere
}
)();
What is special about this kind of syntax? What does ()(); imply?
推荐答案
The creates an anonymous function, closure and all, and the final () tells it to execute itself.
It is basically the same as:
function name (){...}
name();
So basically there is nothing special about this code, it just a 'shortcut' to creating a method and invoking it without having to name it.
This also implies that the function is a one off, or an internal function on an object, and is most useful when you need to the features of a closure.
其他推荐答案
It's an anonymous function being called.
The purpose of that is to create a new scope from which local variables don't bleed out. For example:
var test = 1;
(function() {
var test = 2;
})();
test == 1 // true
One important note about this syntax is that you should get into the habit of terminating statements with a semi-colon, if you don't already. This is because Javascript allows line feeds between a function name and its parentheses when you call it.
The snippet below will cause an error:
var aVariable = 1
var myVariable = aVariable
(function() {/*...*/})()
Here's what it's actually doing:
var aVariable = 1;
var myVariable = aVariable(function() {/*...*/})
myVariable();
Another way of creating a new block scope is to use the following syntax:
new function() {/*...*/}
The difference is that the former technique does not affect where the keyword "this" points to, whereas the second does.
Javascript 1.8 also has a let statement that accomplishes the same thing, but needless to say, it's not supported by most browsers.
其他推荐答案
That is a self executing anonymous function. The () at the end is actually calling the function.
A good book (I have read) that explains some usages of these types of syntax in Javascript is Object Oriented Javascript.
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