A few weeks back, I tweeted that I loved functions that returned functions. I got quite a few replies to the tune of....WTF?! It's important that people understand the value of functions that return functions; using this technique can save you code, JavaScript efficiency, and a gained understanding of how powerful JavaScript can be. I've created a quick example I'd like to show you so that you can get the idea I was trying to communicate.
几周前，我发推文说我喜欢返回函数的函数。 我收到了很多回复…… WTF？ 人们了解返回函数的函数的价值很重要； 使用这种技术可以节省您的代码，JavaScript效率以及对JavaScript强大程度的了解。 我已经创建了一个简单的示例，希望向您展示，以便您可以了解我正在尝试交流的想法。
Let's say you have one host object with two child objects, both with get methods, and both do exactly the same task but with a different attribute:
假设您有一个带有两个子对象的宿主对象，两个子对象都具有get方法，并且两者执行的任务完全相同 ，但属性不同：
var accessors = { sortable: { get: function() { return typeof this.getAttribute('sortable') != 'undefined'; } }, droppable: { get: function() { return typeof this.getAttribute('droppable') != 'undefined'; } } };Repeating the same code isn't ideal, so we could create one external function, passing it an attribute argument:
重复相同的代码并不理想，因此我们可以创建一个外部函数，并为其传递一个属性参数：
function getAttribute(attr) { return typeof this.getAttribute(attr) != 'undefined'; } var accessors = { sortable: { get: function() { return getAttribute('sortable'); } }, droppable: { get: function() { return getAttribute('droppable'); } } };That's a lot better but still not ideal because there's an extra, intermediate function execution every time the method is called. What would work best is a function that returned the final function -- that would eliminate the extra function execution with every call to get:
这样做好很多，但仍然不理想，因为每次调用该方法时，都会执行一个额外的中间函数。 最好的方法是返回最终函数的函数-这样可以避免每次调用get时都要执行额外的函数：
function generateGetMethod(attr) { return function() { return typeof this.getAttribute(attr) != 'undefined'; }; } var accessors = { sortable: { get: generateGetMethod('sortable') }, droppable: { get: generateGetMethod('droppable') } }; /* functional equivalent to the original code: var accessors = { sortable: { get: function() { return typeof this.getAttribute('sortable') != 'undefined'; } }, droppable: { get: function() { return typeof this.getAttribute('droppable') != 'undefined'; } } }; */What you see above is a function returning a function; each method gets its own method for getting the property and there's no overhead upon each get call.
您在上面看到的是一个返回函数的函数； 每个方法都有自己的获取属性的方法，每个get调用都没有开销。
This is a really useful technique that saves you from repeating likewise code and, when used correctly, is easy to understand and maintain!
这是一项非常有用的技术，可以避免重复执行同样的代码，并且如果使用正确，则易于理解和维护！
翻译自: https://davidwalsh.name/javascript-functions
