JS_toString&toValue

/*对象和函数会偷偷调用toString*/
var demo_fun = function(n){
    console.log('per')
}
console.log(demo_fun);
demo_fun.toString = demo_fun.toValue = function(){
    console.log('Run toString , Run toValue');
    return 'demo_fun'
}
console.log(demo_fun);
var demo_obj = {
    i:10
}
console.log(demo_obj);
demo_obj.toString = demo_obj.toValue = function(){
    console.log('Run toString , Run toValue');
    return 'demo_obj';
}
console.log(demo_obj);

/*题目*/
function add(n){
    var res = n;
    var fun = function(n){
        res += n;
        return fun;
    }
    fun.toString = fun.valueOf = function(){return res}
    return fun;
}
var a = add(1)(2)(3)(4);
console.log(a);

 

转载于:https://www.cnblogs.com/somesayss/archive/2013/03/07/2948796.html