function _new(fn, ...arg) {
const obj = Object.create(fn.prototype);
const ret = fn.apply(obj, arg);
return ret instanceof Object ? ret : obj;
}
var Dog = function(name) {
this.name = name
}
Dog.prototype.bark = function() {
console.log('wangwang')
}
Dog.prototype.sayName = function() {
console.log('my name is ' + this.name)
}
var simao = _new(Dog, 'simao')
simao.bark()
simao.sayName()
console.log(simao instanceof Dog) // true
