为什么函数用括号括起来？ [英] Why is the function with in parenthesis?

问题描述

问题：

为什么函数包含在括号中？我已经从括号中取出了这个代码，它没有任何问题。

Why is the function wrapped in a parenthesis? I have taken this code out of parenthesis and it works with no trouble.

将代码放入（function（）{...这里的代码...}）（）;喜欢它在以下示例中？

What is the benefit of having the code in a (function() { ...Code Here...})(); like it is in the following example?

代码：

(function() {
    "use strict";
    // Doesn't work because strict mode 
    // enforces the fact that the second example shouldn't work
    if (true) {
        function fn1() {
            // This won't run
            console.log("doesn't work -- have a great Die Hard Day XIII");
        };
        fn1();
    }
})();

代码这里：将JQuery字作为参数发送给这个命名空间的是什么。我知道函数包含在（...）中的原因是创建一个命名空间。我想一个更好的问题是为什么一个人会传入一个变量，但我想这将是另一个命名空间需要变量的情况。

Code Here: What would sending the JQuery word as a parameter do for this namespace. I know that the reason that the function is enclosed in (...) is to create a namespace. I guess a better question would be as to why one would pass in a variable, but I would imagine that would be in case another namespace needed the variable.

( function( $ ) {
    // Init Skrollr
    var s = skrollr.init({
        render: function(data) {
            //Debugging - Log the current scroll position.
            //console.log(data.curTop);
        }
    });
} )( jQuery );

推荐答案

我采取了这个括号内的代码，没有问题。

I have taken this code out of parenthesis and it works with no trouble.

这不正确;它本身无法运行（甚至无法解析）。 JavaScript在函数声明所在的位置看到函数并假设它是函数声明。括号用于强制上下文成为表达式。如果它明确地是一个函数文字 - 例如，在变量声明中 - 但许多人发现它更具可读性，那么这种做法是多余的。例如，有一个 jsHint选项来强制执行。

That’s not correct; it can’t run (or even be parsed) by itself. JavaScript sees function in a place where a function declaration can be and assumes it’s a function declaration. Parentheses are used to force the context to be an expression. The practice is redundant if it’s unambiguously a function literal – say, in a variable declaration – but many find it more readable. There’s a jsHint option to enforce it, for example.

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