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| function isType (type) { | |
| return function (arg) { | |
| return typeof(arg) === type; | |
| }; | |
| } | |
| function instanceOf (clazz) { | |
| return function (arg) { | |
| return arg instanceof clazz; | |
| }; | |
| } | |
| function isPrototypeOf (proto) { | |
| return Object.prototype.isPrototypeOf.bind(proto); | |
| } | |
| function check () { | |
| var matchers = [].slice.call(arguments, 0, arguments.length - 1), | |
| body = arguments[arguments.length - 1]; | |
| return function () { | |
| var i, | |
| arg, | |
| value; | |
| if (arguments.length != matchers.length) return; | |
| for (i in arguments) { | |
| arg = arguments[i]; | |
| if (!matchers[i].call(this, arg)) return; | |
| } | |
| value = body.apply(this, arguments); | |
| return value === undefined | |
| ? null | |
| : value; | |
| } | |
| } | |
| function appendable (fns) { | |
| var i, | |
| value, | |
| fn; | |
| if (fns === undefined) fns = []; | |
| function firstSuccess () { | |
| for (i in fns) { | |
| value = fns[i].apply(this, arguments); | |
| if (value !== undefined) return value; | |
| } | |
| } | |
| firstSuccess.appendChecked = function () { | |
| return appendable(fns.concat([check.apply(this, arguments)])); | |
| } | |
| return firstSuccess; | |
| } | |
| function MultipleDispatch () { | |
| return appendable().appendChecked.apply(this, arguments); | |
| } | |
| ////////// EXAMPLE ////////// | |
| function Fighter () {}; | |
| function Meteor () {}; | |
| var handlesManyCases = MultipleDispatch( | |
| instanceOf(Fighter), instanceOf(Meteor), | |
| function (fighter, meteor) { | |
| return "a fighter has hit a meteor"; | |
| } | |
| ).appendChecked( | |
| instanceOf(Fighter), instanceOf(Fighter), | |
| function (fighter, fighter) { | |
| return "a fighter has hit another fighter"; | |
| } | |
| ).appendChecked( | |
| instanceOf(Meteor), instanceOf(Fighter), | |
| function (meteor, fighter) { | |
| return "a meteor has hit a fighter"; | |
| } | |
| ).appendChecked( | |
| instanceOf(Meteor), instanceOf(Meteor), | |
| function (meteor, meteor) { | |
| return "a meteor has hit another meteor"; | |
| } | |
| ); | |
| handlesManyCases(new Meteor(), new Meteor()); | |
| //=> 'a meteor has hit another meteor' | |
| handlesManyCases(new Fighter(), new Meteor()); | |
| //=> 'a fighter has hit a meteor' |
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