オーバーロードする

overload.js

function overload(args, fns){
	var result = null
	fns.some(fn => {
		if(Array.isArray(fn)){
			fn = {type: fn[0], function: fn[1]}
		}
		if(fn.type == null || fn.type.every((reqtype, i) => typeMatch(reqtype, args[i]))){
			result = fn.function(...args)
			return true
		}
		return false
	})
	return result
	
	function typeMatch(reqtype, realdata){
		if(typeof reqtype === "function"){
			return reqtype(realdata)
		}
		if(Array.isArray(reqtype)){
			return reqtype.some(e => typeMatch(e, realdata))
		}
		if(typeof reqtype === "string"){
			return typeof realdata === reqtype || (typeof window[reqtype] === "function" && realdata instanceof window[reqtype])
		}
		
		return false
	}
}

usage.js

function abc(){
	overload(arguments, [
		{
			type: ["number", "number", "number", "number"],
			function: (a,b,c,d) => {console.log("num4",a,b,c,d)}
		},{
			type: ["number", "number"],
			function: (a,b) => {console.log("num2",a,b)}
		},{
			type: ["number", "number", "number"],
			function: (a,b,c) => {console.log("num3",a,b,c)}
		},{
			type: ["number", "string"],
			function: (a,b) => {console.log("num-str",a,b)}
		},{
			type: ["Object", ["string","Array"]],
			function: (a,b) => {console.log("obj-(str-array)",a,b)}
		},{
			type: null,
			function: _ => {console.log("no match")}
		}
	])
}

console.log("--")
abc()
console.log("--")
abc(1,2,3,4)
console.log("--")
abc(1,2)
console.log("--")
abc(1,2,3)
console.log("--")
abc(1,"abc")
console.log("--")
abc({a:1},[4,5])
console.log("--")
abc({a:1},"abc")
console.log("--")

/*
--
no match
--
num4 1 2 3 4
--
num2 1 2
--
num2 1 2
--
num-str 1 abc
--
obj-(str-array) Object {a: 1} [4, 5]
--
obj-(str-array) Object {a: 1} abc
--
*/



function x(){
	return overload(arguments, [
		{
			type: ["string", "string", "Object", "function"],
			function: fn
		},{
			type: ["string", "function"],
			function: (a,b) => fn("", a, {}, b)
		},{
			type: ["string", "Object"],
			function: (a,b) => fn("", a, b, _ => {})
		},{
			type: null,
			function: _ => {console.log("引数が不正です")}
		}
	])

	function fn(target, value, option, cb){
		// なにか
	}
}

function y(){
	overload(arguments, [
		[
			["Array"],
			a => fn({x: a[0], y: a[1]})
		],[
			["Object"],
			x => fn(x)
		]
	])
	
	function fn(obj){
		// obj.x
		// obj.y
	}
}