[原创]一个js函数重载功能——

本文介绍如何在JavaScript中创建自定义函数并实现类型转换，包括如何使用switch语句和定义函数的类型。

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;;;void function(window, undefined){
var $ = {
        now:(new Date()).getTime(),
        type2string:{},
        type:function(s){
return s == null ? 'empty' : ($.type2string[Array.prototype.toString.call(s)] || 'object');
        },
switch:function(){
var args = Array.prototype.slice.call(arguments), fn = this;
var i = 0, p , ff = fn[$.now], path = '';
while(p = args[i++]){ path += $.type(p) + ','; }
if(path){ ff = ff[path] }else{ ff = ff['fn'] }
if($.type(ff)!='function'){ 
if(ff=fn[$.now]['fn']){
return ff.apply(fn,args);
                }
throw new Error('function undefined!');
            }
return ff.apply(fn,args);
        },
        defined:function(type,fn,source){
var types = fn[$.now];
if(!types){ types = fn[$.now] = {} }
if($.type(type)=='function'){
                types['fn'] = type;
return fn;
            }
            types[type + ','] = source;
return fn;
        }
    };
    ('Object,Function,String,Number,Boolean,Date,RegExp').replace(/[^,]+/g,function(a){
        $.type2string['[object ' + a + ']'] = a.toLowerCase();
    });
    window.fn = {
        defined:function(type,f){
var fn = function(){ return $.switch.apply(fn,arguments); };
            $.defined(type,fn,f);
            fn['defined'] = function(type,f1){ return $.defined(type,fn,f1); };
return fn;
        }
    };
}(this);
var a = fn.defined(function(a,b){
    alert([a,b])
}).defined('string,string',function(s1,s2){
    alert(['string|string',s1,s2]);
}).defined('string,object',function(s,o){
    alert(['string|object',s,o])
});
a('1');
a('1','2');
a('1',{});
a('1',true);