我使用 John Resig 的 class.js:
/* Simple JavaScript Inheritance
* By John Resig http://ejohn.org/
* MIT Licensed.
*/
// Inspired by base2 and Prototype
var initializing = false, fnTest = /xyz/.test(function(){xyz;}) ? /\b_super\b/ : /.*/;
// The base Class implementation (does nothing)
Class = function() {};
// Create a new Class that inherits from this class
Class.extend = function(prop) {
var _super = this.prototype;
// Instantiate a base class (but only create the instance,
// don't run the init constructor)
initializing = true;
var prototype = new this();
initializing = false;
// Copy the properties over onto the new prototype
for (var name in prop) {
// Check if we're overwriting an existing function
prototype[name] = typeof prop[name] == "function" &&
typeof _super[name] == "function" && fnTest.test(prop[name]) ?
(function(name, fn){
return function() {
var tmp = this._super;
// Add a new ._super() method that is the same method
// but on the super-class
this._super = _super[name];
// The method only need to be bound temporarily, so we
// remove it when we're done executing
var ret = fn.apply(this, arguments);
this._super = tmp;
return ret;
};
})(name, prop[name]) :
prop[name];
}
// The dummy class constructor
Class = function () {
// All construction is actually done in the init method
if ( !initializing && this.init )
this.init.apply(this, arguments);
}
// Populate our constructed prototype object
Class.prototype = prototype;
// Enforce the constructor to be what we expect
Class.constructor = Class;
// And make this class extendable
Class.extend = arguments.callee;
return Class;
};
if(!(typeof exports === 'undefined')) {
exports.Class = Class;
}
如何使用它在新类中声明静态变量?
最佳答案
如果“静态”是指类范围内的,则只需将其分配为“类”(构造函数)上的属性,例如:
var Thingy = Class.extend({
init: function() {
// ...
}
});
Thingy.myStaticVariable = "foo";
使用时必须使用完全限定名称。
当然,您可以通过创建关闭的上下文来创建“静态”变量:
var Thingy = (function() {
var myStaticVariable = "foo";
return Class.extend({
init: function() {
// ...
}
});
});
...然后它是 A) 真正私有(private)于您的“类”,并且 B) 无需类前缀即可使用。
<小时/>如果不提及 Resig 的 SJI 非常基础且相当过时,这个主题的答案就不会真正完整。如今,我建议使用 ES2015 (ES6) 语义和一个不错的转译器(我使用 Babel )。坦率地说,我对 SJI 使用函数反编译来处理 super 调用一直不满意,特别是因为它不严格,并且很容易被字符串文字中出现的“ super ”一词混淆,所以我 wrote my own thing instead (现在 ES2015 也已过时)。但有趣的是,ES2015 类语义仅提供静态方法,而不是静态变量,因此您最终会执行与上述相同的操作:
class Thingy {
constructor() {
// ...
}
});
Thingy.myStaticVariable = "foo";
或
let Thingy = (function() {
let myStaticVariable = "foo";
class Thingy {
constructor() {
// ...
}
}
return Thingy;
})();
关于javascript - 如何用class.js声明静态变量?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/33311091/