Standardized class syntax
is coming
in ECMAScript 6, supposedly, but until then I need a class factory that fills the gap.
For me that means (in no particular order):
- prototypal inheritance under the hood
- access to overridden properties (
super) - inheritance of
staticproperties staticconstructors- close correspondence to ES6 syntax
- ES5/browser compatibility
- only-pay-for-what-you-use performance
- excellent test coverage:
I have no delusions of persuading the world to use this tool. Just try
npm search inheritance some time to see how many other people have come
up with solutions that work for them.
If you have a special interest in the tired me-too sport of pure-JavaScript class factory implementations, you might find this one interesting for its solutions to each of the requirements listed above, particularly the lazy (just-in-time) population of prototype properties.
Note that I did not mention privacy enforcement as a requirement. If you
need a mechanism like the private keyword in other languages, I have a
separate project that works
seamlessly alongside this one.
From NPM:
npm install cls
From GitHub:
cd path/to/node_modules
git clone git://github.com/benjamn/cls.git
cd cls
npm install .
One example will have to suffice for now:
var cls = require("cls");
var BaseClass = cls.extend({
init: function(a, b) {
this.sum = a + b;
},
getSum: function() {
return this.sum;
},
statics: {
name: "BaseClass",
init: function(cls) {
cls.zero = new cls(0, 0);
}
}
});
var SubClass = BaseClass.extend({
init: function(arg) {
this._super(arg, arg);
this.sum += 1;
},
statics: {
name: "SubClass"
}
});
assert(BaseClass.name === "BaseClass");
assert(SubClass.name === "SubClass");
assert(new BaseClass(2).getSum() === 4);
assert(new SubClass(2).getSum() === 5);
assert(SubClass.zero !== BaseClass.zero);
assert(SubClass.zero instanceof SubClass);
assert(SubClass.zero.getSum() === 1);For more complex examples, see test/run.js.
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