JavaScript中的动态实例化

Question

除了eval之外,还有其他方法可以使用变量参数列表来实例化对象吗？

例如: var foo = instantiate(className, [arg1, arg2, ...])

Answer 1

您可以使用可变参数列表实例化对象,如下所示:

function instantiate(className, args) {
    var o, f, c;
    c = window[className]; // get reference to class constructor function
    f = function(){}; // dummy function
    f.prototype = c.prototype; // reference same prototype
    o = new f(); // instantiate dummy function to copy prototype properties
    c.apply(o, args); // call class constructor, supplying new object as context
    o.constructor = c; // assign correct constructor (not f)
    return o;
}

附注:您可能希望直接引用类构造函数:

var foo = instantiate(Array, [arg1, arg2, ...]);
// Instead of:
var foo = instantiate("Array", [arg1, arg2, ...]);

...这使得它与非全局函数兼容.

Answer 2

在ES5中使用Object.create():

function instantiate(constructor, args) {
    var instance = Object.create(constructor.prototype);
    constructor.apply(instance, args);
    return instance;
}

在ES6中使用扩展运算符:

var foo = new constructor(...args);