javascript 如何正确返回空函数？
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/17026092/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
How to properly return an empty function?
提问by Frédéric Hamidi
I'm using a run-time assignment of functions to account for browser differences. However for un-supported browsers, I want to return an empty function so that a JavaScript error is not thrown.
我正在使用功能的运行时分配来解决浏览器差异。但是，对于不受支持的浏览器，我想返回一个空函数，以免引发 JavaScript 错误。
But, jslint complains about empty functions. What is the jslint happy way to do this?
但是，jslint 抱怨空函数。什么是 jslint 快乐的方式来做到这一点？
Empty block.
空块。
$R.functionNull = function () {
// events not supported;
};
$R.Constructor.prototype.createEvent = (function () {
if (doc.createEvent) {
return function (type) {
var event = doc.createEvent("HTMLEvents");
event.initEvent(type, true, false);
$NS.eachKey(this, function (val) {
val.dispatchEvent(event);
});
};
}
if (doc.createEventObject) {
return function (type) {
var event = doc.createEventObject();
event.eventType = type;
$NS.eachKey(this, function (val) {
val.fireEvent('on' + type, event);
});
};
}
return $R.functionNull;
}());
回答by Frédéric Hamidi
You can add a body to your function and have it return undefined:
您可以向您的函数添加一个主体并让它返回undefined：
$R.functionNull = function() {
// Events not supported.
return undefined;
};
This keeps the same semantics as a "truly empty" function, and should satisfy JSLint.
这与“真正的空”函数保持相同的语义，并且应该满足 JSLint。
回答by Nano Miratus
For me this works best:
对我来说，这最有效：
emptyFunction = Function();
console.log(emptyFunction); // logs '? anonymous() {}'
console.log(emptyFunction()); // logs 'undefined'
It's so short that I wouldn't even assign it to a variable (of course you can also use a constant-like variable "EF" or so, that's even shorter and doesn't need the additioal "()" brackets). Just use "Function()" anywhere you need a truly empty function, that doesn't even have a name, not even when you assign it to a variable, and that's the small behaviour difference between my solution and Frédéric's:
它太短了，我什至不会将它分配给一个变量（当然，你也可以使用类似常量的变量“EF”左右，它更短，不需要额外的“()”括号）。只需在需要真正空函数的任何地方使用“Function()”，该函数甚至没有名称，即使将其分配给变量时也不行，这就是我的解决方案与 Frédéric 的解决方案之间的微小行为差异：
// --- Frédéric ---
emptyFunction = function() {
return undefined;
}
console.log(emptyFunction.name); // logs '"emptyFunction"'
// --- me ---
emptyFunction = Function();
console.log(emptyFunction.name); // logs '""' (or '"anonymous"' in chrome, to be fair)
回答by splintor
Use the lambda expression:
使用 lambda 表达式：
$R.functionNull = () => void 0;
回答by Michal ?ervenka
What about returning
回来怎么办
return () => undefined;
return () => undefined;
instead of
代替
return $R.functionNull;
return $R.functionNull;
