javascript ES6 动态类名
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ES6 Dynamic class names
提问by simon-p-r
I have been experimenting with ES6 classes and am wondering if you can change class names dynamically? For example
我一直在试验 ES6 类，想知道您是否可以动态更改类名？例如
class [Some dynamic name] {};
采纳答案by Felix Kling
There is probably a better solution for whatever you are trying to achieve, but you can assign a class expression to an object:
对于您想要实现的任何目标，可能都有更好的解决方案，但您可以为对象分配一个类表达式：
let classes = {};
classes[someName] = class { ... };
This didn't really change in ES2015: if you want to create a dynamically named binding, you have to use an object or some other mapping instead.
这在 ES2015 中并没有真正改变：如果你想创建一个动态命名的绑定，你必须使用一个对象或其他一些映射来代替。
回答by Panu Logic
let C = class
{ // ...
}
Object.defineProperty (C, 'name', {value: 'TheName'});
// test:
let itsName = (new C()).constructor.name;
// itsName === 'TheName' -> true
回答by Daerdemandt
There is a pretty simple way to do it:
有一个非常简单的方法来做到这一点：
const nameIt = (name, cls) => ({[name] : class extends cls {}})[name];
Here's the demo.
这是演示。
It uses an object literal to define a field with a desired name that would hold a new class. This causes the new class to automatically get the desired name. After we're done with that, we extract that new class and return it.
它使用对象字面量来定义一个具有所需名称的字段，该字段将包含一个新类。这会导致新类自动获得所需的名称。完成后，我们提取该新类并将其返回。
Note the parens around the object literal, so that curly braces don't get mistaken for a code block (...) => {...}.
注意对象字面量周围的括号，以免花括号被误认为是代码块(...) => {...}。
Of course, putting an existing class into named fields won't change the class, so this only works if you are creating a new class. If you only need a dynamic name in one place where you define the class you are naming, you can drop an extra inheritance and just go:
当然，将现有类放入命名字段不会更改该类，因此这仅在您创建新类时才有效。如果您只需要在定义要命名的类的地方使用动态名称，则可以删除额外的继承，然后继续：
const myClass = {[name]: class {
...
}}[name];
回答by Anibal Ambertin
To take it a bit further playing with dynamic class names and dynamic inheritance, when using babel you can just do something like this:
为了更深入地使用动态类名和动态继承，在使用 babel 时，您可以执行以下操作：
function withname(name, _parent) {
return class MyDinamicallyNamedClass extends (_parent||Object) {
static get name() { return name || _parent.name }
}
}
回答by trusktr
One way, even if not ideal, is simple with eval:
一种方法，即使不理想，也很简单eval：
~function() {
const name = "Lorem"
eval(`
var ${name} = class ${name} {}
`)
console.log(Lorem) // class Lorem {}
}()
Note, it has to be with var. Using let, const, and plain classinside the evalwon't work.
请注意，它必须与var. 在里面使用let, const, 和 plainclass是eval行不通的。
Another way with Function:
另一种方式Function：
~function() {
const name = "Lorem"
const c = new Function(`
return class ${name} {}
`)()
console.log(c) // class Lorem {}
}()
Sitenote: you can pass scope variables into the Functionand use them inside:
站点注意：您可以将范围变量传递到Function并在其中使用它们：
~function() {
const name = "Lorem"
const val = "foo"
const Class = new Function('val', `
return class ${name} {
constructor() {
console.log( val )
}
}
`)( val )
console.log(Class) // class Lorem {}
new Class // "foo"
}()
回答by Greg Woz
The example with which I struggled - resolved in the way below:
我挣扎的例子 - 按以下方式解决：
const models = {
route: mongoose.model('Route'),
company: mongoose.model('Company'),
...
}
and then:
接着：
const name = 'route'
const record = new models[name]()
