函数上的额外括号 [英] Extra parentheses on function

问题描述

可能重复：



这个函数（function（）{}）;在括号中，意味着在javascript？

Javascript函数

我遇到类似这样的标记：

I encountered markup similar to this:

var something = (function(){
    //do stuff
    return stuff;
})()
document.ondblclick = function(e) { alert(something(e)) };

我不明白开头（并在 something 变量中关闭）（）。

I don't understand the opening ( and closing )() in the something variable. Could you explain the difference to writing it like this?

var something = function(){
    //do stuff
    return stuff;
};

$ b

谢谢！

Thanks!

推荐答案

这可能更容易理解，如果你离开冗余的括号，因为他们没有目的：

It's probably easier to understand if you leave the redundant parens out because they serve no purpose:

var something = function() {
    return 3;
} // <-- a function. 
(); // now invoke it and the result is 3 (because the return value is 3) assigned to variable called something 

console.log(something) //3 because the function returned 3 

var something = function() {
    return 3;
}; // a function is assigned to a variable called something

console.log(something) //logs the function body because it was assigned to a function
console.log(something()) //invoke the function assigned to something, resulting in 3 being logged to the console because that's what the function returns

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