js 基础

 

  <script>
      document.cookie = "a=1";
      document.cookie;
      console.log("parseInt(1)", parseInt("1"));
      //遇到不能转换的就转换了
      console.log("parseInt(12a)", parseInt("12a"));
      console.log("parseInt(1.22)", parseFloat("1.22"));

      console.log("String(1.333)", String(1.333));

      console.log("Number(NaN)", Number(NaN));
      console.log("Number(true)", Number(true));
      console.log("Number(false)", Number(false));

      console.log("Boolean(null)=", Boolean(null));
      console.log("Boolean(undefined)=", Boolean(undefined));
      console.log("Boolean('')=", Boolean(""));
      console.log("Boolean(NaN)=", Boolean(NaN));

      console.log("Boolean(0)=", Boolean(0)); // false
      console.log("Boolean(1)=", Boolean(1)); // true
      console.log("Boolean(-1)=", Boolean(-1)); // true

      if (null == null) {
        console.log("null == null", true);
      }

      if (undefined == undefined) {
        console.log("undefined==undefined", true);
      }
      if (null == undefined) {
        console.log("null==undefined", true);
      }

      if (NaN == NaN) {
        console.log("NaN == NaN", true);
      }

      //类型转换 双等号 比较是要做类型转换
      console.log("Boolean(1)=", Boolean(1)); // true
      console.log("Boolean('1')=", Boolean("1")); // true
      //将字符传转换为数字进行比较
      if (1 == "1") {
        console.log("1=='1'", true);
      }
      //三个等号比较 比较类型 和 值
      if (1 === "1") {
        console.log("1==='1'", true);
      }

      function DoSomething() {}
      console.log("DoSomething.prototype", DoSomething.prototype);
      console.log(DoSomething.toString());

      function User(name, age) {
        this.name = name;
        this.age = age;
        this.Fait = function () {
          console.log(this.name + "在战斗");
        };
      }

      User.prototype.Addr = "中国";

      function Soldier() {}

      let user = new User("上等兵", 12);
      //先找实例对象的方法 实例对象没有去构造函数中查找 构造函数中没有 去原型对象中查找
      user.Fait = function () {
        console.log("我是士兵" + this.name + "在战斗");
      };
      console.log("user.name", user.name);
      user.Fait();

      // User.prototype.Say=function(){
      //   console.log(this.name+"说你好")
      // }
      // function Solider(name, age) {
      //   User.call(this, name, age);
      //   this.SoliderFailt = function () {
      //     console.log("士兵在战斗"+this.name );
      //   };
      // }

      // Solider.prototype = new User()
      // let solider =new Solider("公民")
      // solider.Say()
      // solider.SoliderFailt()
      // solider.Fait()
      // let user = new User("pp", 12);
      // console.log("User.prototype", User.prototype);
      // console.log("user.name", user.name);
      // console.log("user.__proto__", user.__proto__);

      function Anmail(name, age) {
        this.name = name;
        this.age = age;
        this.Say = function () {
          console.log("name=" + name + "-" + "age" + age);
        };
      }

      function Loin(name, age) {
        this.name = name;
        this.age = age;
        Anmail.call(this, name, age);
        this.LoinSay = function () {
          console.log("Loinname=" + name + "-" + "age" + age);
        };
      }

      console.log("Anmail.prototype", Anmail.prototype);
      Loin.prototype = Object.create(Anmail.prototype);
      // Loin.prototype = new Anmail()
      // Loin.prototype.constructor = Loin

      var loin = new Loin("狮子", 12);
      loin.Say();

      console.log("Loin.prototype", Loin.prototype);
      console.log(Loin.prototype.constructor);
    </script>