# javascript 基础测试题(二)

class Drop {
  constructor(selector) {
    this.state = 0;
    this.offsetL = null;
    this.offsetT = null;
    this.div = document.querySelector(selector);
  }
  init() {
    this.div.onmousedown = function(e) {
      this.offsetL = e.offsetX;
      this.offsetT = e.offsetY;
      this.state = 1;
    };
    this.div.onmouseup = function() {
      this.state = 0;
    };
    this.div.onmousemove = function(e) {
      if (this.state === 1) {
        var clinetX = e.clientX;
        var clinetY = e.clientY;
        this.style.left = clinetX - this.offsetL + "px";
        this.style.top = clinetY - this.offsetT + "px";
      }
    };
  }
}
const drop = new Drop("#d");
drop.init();

function simpleClone(json) {
  var obj = {};
  for (var i in json) {
    obj[i] = json[i];
  }
  return obj;
}
var obj = {
  a: "hello",
  b: {
    a: "world",
    b: 21
  },
  c: ["Bob", "Tom", "Jenny"],
  d: function() {
    alert("hello world");
  }
};
var cloneObj = simpleClone(obj);
console.log(cloneObj.b);
console.log(cloneObj.c);
console.log(cloneObj.d);
cloneObj.b.a = "changed";
cloneObj.c = [1, 2, 3];
cloneObj.d = function() {
  alert("changed");
};
console.log(obj.b);
console.log(obj.c);
console.log(obj.d);

function deepClone(json) {
  var obj = {};
  for (var i in json) {
    if (typeof json[i] === "object") {
      obj[i] = deepClone(json[i]);
    } else {
      obj[i] = json[i];
    }
  }
  return obj;
}
var obj = {
  a: "hello",
  b: {
    a: "world",
    b: 21
  },
  c: ["Bob", "Tom", "Jenny"],
  d: function() {
    alert("hello world");
  }
};
var cloneObj = deepClone(obj);
console.log(cloneObj.b);
console.log(cloneObj.c);
console.log(cloneObj.d);
cloneObj.b.a = "changed";
cloneObj.c = [1, 2, 3];
cloneObj.d = function() {
  alert("changed");
};
console.log(obj.b);
console.log(obj.c);
console.log(obj.d);

Array.prototype.myMap = function(fn, ctx) {
  let oriArr = Array.prototype.slice.call(this);
  let mappedArr = [];
  for (let i = 0; i < oriArr.length; i++) {
    if (!oriArr.hasOwnProperty(i)) {
      // 若原数组为稀疏数组，不含索引为i的元素时，mappedArr直接增加length，来达到同样的稀疏效果
      mappedArr.length++;
    } else {
      mappedArr.push(fn.call(ctx, oriArr[i], i, this));
    }
  }
  return mappedArr;
};
console.log([1, , , , 3].myMap(val => val + 1));

if (!Array.prototype.map) {
  Array.prototype.map = function(callback, thisArg) {
    var T, A, k;

    if (this == null) {
      throw new TypeError(" this is null or not defined");
    }

    // 1. 将O赋值为调用map方法的数组.
    var O = Object(this);

    // 2.将len赋值为数组O的长度.
    var len = O.length >>> 0;

    // 3.如果callback不是函数,则抛出TypeError异常.
    if (Object.prototype.toString.call(callback) != "[object Function]") {
      throw new TypeError(callback + " is not a function");
    }

    // 4. 如果参数thisArg有值,则将T赋值为thisArg;否则T为undefined.
    if (thisArg) {
      T = thisArg;
    }

    // 5. 创建新数组A,长度为原数组O长度len
    A = new Array(len);

    // 6. 将k赋值为0
    k = 0;

    // 7. 当 k < len 时,执行循环.
    while (k < len) {
      var kValue, mappedValue;

      //遍历O,k为原数组索引
      if (k in O) {
        //kValue为索引k对应的值.
        kValue = O[k];

        // 执行callback,this指向T,参数有三个.分别是kValue:值,k:索引,O:原数组.
        mappedValue = callback.call(T, kValue, k, O);

        // 返回值添加到新数组A中.
        A[k] = mappedValue;
      }
      // k自增1
      k++;
    }

    // 8. 返回新数组A
    return A;
  };
}

let newInstanceof = function(leftVal, RightVal) {
  let objProto = leftVal.__proto__;
  while (objProto) {
    if (objProto == RightVal.prototype) {
      return true;
    }
    objProto = objProto.__proto__;
  }
  return false;
};

if (!Funtion.prototype.bind) {
  Funtion.prototype.bind = function(oThis) {
    if (typeof this !== "function") {
      throw new TypeError(
        "Function.prototype.bind - what is trying to be bound is not callable"
      );
    }
    var args = Array.prototype.slice.call(arguments, 1),
      fToBind = this,
      fNOP = function() {},
      fBound = function() {
        return fToBind.apply(
          this instanceof fBound ? this : oThis,
          args.concat(Array.prototype.slice.call(arguments))
        );
      };
    if (this.prototype) {
      fNOP.prototype = this.prototype;
    }
    fBound.prototype = new fNOP();
    return fBound;
  };
}

Function.prototype.call2 = function(context) {
  var context = context || window;
  context.fn = this;

  var args = [];
  for (var i = 1, len = arguments.length; i < len; i++) {
    args.push("arguments[" + i + "]");
  }

  var result = eval("context.fn(" + args + ")");

  delete context.fn;
  return result;
};

// 测试一下
var value = 2;

var obj = {
  value: 1
};

function bar(name, age) {
  console.log(this.value);
  return {
    value: this.value,
    name: name,
    age: age
  };
}

bar.call2(null); // 2

console.log(bar.call2(obj, "kevin", 18));

function _new(fn, ...args) {
  let obj = {};
  // obj.__proto__ = fn.prototype;  与setPrototypeOf 等价，推荐使用setPrototypeOf
  Object.setPrototypeOf(obj, fn.prototype);
  let result = fn.apply(obj, args);
  return result instanceof Object ? result : obj;
}
function Test(name, age) {
  this.name = name;
  this.age = age;
}
Test.prototype.sayName = function() {
  console.log(this.name);
};

let test = _new(Test, "zxy", 25);
console.log(test.name);
console.log(test.age);
test.sayName();