javascript中借用别的类的方法

借用别的类的方法

/**
 * Created by Administrator on 2015/12/23.
 */
//====================借用方法===============================
function borrowMethods(borrowFrom,addTo){
    var from = borrowFrom.prototype;
    var to = addTo.prototype;
    for(m in from){
        if(typeof from[m]!="function"){
            continue;
        }
        to[m] = from[m];
    }
}

// 带有通用的toString()方法的类
function GenericToString(){}
GenericToString.prototype.toString = function(){
    var props = [];
    for(var name in this){
        if(!this.hasOwnProperty(name)) continue;
        var value = this[name];
        var s = name+":";
        switch (typeof value){
            case "function": s+="function";
                break;
            case "object":
                if(value instanceof Array) s+="array";
                else s+=value.toString();
                break;
            default :
                s += String(value);
                break;
        }
        props.push(s);
    }
    var str = "";
    if(props.length>0){
        str+="[";
        for(i=0;i<props.length;i++){
            str += props[i];
            if(i<props.length-1){
                str+=",";
            }
        }
        str +="]";
    }
    return str;
}
// 带有通用的equals()方法的类
function GenericEquals(){}
GenericEquals.prototype.equals = function(that){
    if(this == that){
        return true;
    }
    var propsInThat = 0;
    for(var name in that){
        propsInThat++;
        //如果属性值不相同，返回false
        if(this[name]!==that[name]){
            return false;
        }
    }
    var propsInThis =0;
    for(name in this) propsInThis ++;
    //判断属性个数是否相等
    if(propsInThat != propsInThis){
        return false;
    }
    return true;
}

//声明Rectangle类
function Rectangle(w, h) {
    this.width = w;
    this.height = h;
}
Rectangle.prototype.area = function () {
    return this.width * this.height;
}
borrowMethods(GenericToString,Rectangle);
borrowMethods(GenericEquals,Rectangle);

var rectangle = new Rectangle(50,100);
console.log(rectangle.toString());

console.log(rectangle instanceof Object);
console.log(rectangle instanceof  Rectangle);
console.log(rectangle.constructor == Object);
console.log(rectangle.constructor == Rectangle);

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