var a = {a:"haha",getA:function(){console.log(this.a);}
}
var b = {a:"hello"}
var getA = a.getA;
var getA2 = getA.bind(a);
function run(fn){fn();
}
//分别输出
a.getA();//haha
getA();//window下面的a对象
run(a.getA);//window下面的a对象
getA2.call(b);//haha

var demoObj = {a:1,b:{fun:function(){console.log(this.a); }}
}
demoObj.b.fun();//undefined，因为this指向demoObj.b，b里面没有a

var demoObj = {a:1,b:{fun:function(){console.log(this.a); }}
}
var newFun = demoObj.b.fun;
newFun();//undefined，this指向window

function Fun(){this.name = "haha";
}
var stu = new Fun();
console.log(stu.name); //haha

//例1
function Fun()
{  this.name = 'haha';  return {};
}
var stu = new Fun();
console.log(stu.name); //undefined，stu为{}

//例2
function Fun()
{  this.name = 'haha';  return function(){};
}
var stu = new Fun();
console.log(stu.name); //undefined

//例3
function Fun()
{  this.name = 'haha';  return 123;
}
var stu = new Fun();
console.log(stu.name); //haha，stu为Fun的实例

//例4
function Fun()
{  this.name = 'haha';  return undefined;
}
var stu = new Fun();
console.log(stu.name); //haha

//例5
function Fun()
{  this.name = 'haha';  return null;
}
var stu = new Fun();
console.log(stu.name); //haha

getA.call(b);//hello
getA.call(a);//haha

var getA2 = getA.bind(a);

getA2.call(b);//haha
//相当于a.getA.call(b);

var getA2 = getA.bind(a);
var getA3 = getA.bind(b);
getA2.call(b);//haha
getA3.call(b);//hellovar getA2 = getA.bind(a);
var getA3 = getA2.bind(b);
getA2.call(b);//haha
getA3.call(b);//haha

var a = {a:"haha",getA:function(){this.c = "12345678";console.log(this,this.a);}
}
var b = {a:"hello"}
var getA = a.getA;
var getA2 = getA.bind(a);
var getA3 = getA2.bind(b);
var getObj = new getA3();//new一下，this就是当前构造函数的实例
getA3();//其他情况，this一直被静态绑定为a

Math.max()    //只接收单独的参数，通过下面的方法可以在数组上面使用max方法：
Math.max.apply(null, array)；    //会将array数组参数展开成单独的参数再传入
Array.prototype.push.apply(arr1,arr2);    //将一个数组拆开push到另一个数组中；不用apply则会将后续数组参数当成一个元素push进去。
Array.prototype.slice.call(arguments);    //在类素组对象上使用slice方法
function isArray(obj){return Object.prototype.toString.call(obj) === '[object Array]' ;
}    //验证是否是数组

//原来的函数有4个参数
var displayArgs = function (val1, val2, val3, val4) {console.log(val1 + " " + val2 + " " + val3 + " " + val4);
}
var emptyObject = {};
// 生成新函数时bind方法指定了2个参数，则新函数会带着这个两个实参
var displayArgs2 = displayArgs.bind(emptyObject, 12, "a");
// 调用时传入另2个参数，要在bind方法传入的2个实参后面
displayArgs2("b", "c");
// Output: 12 a b c

var demoObj = {name:"haha",fun:function(a,b,c){console.log(a,b,c);}
}
var newFun = demoObj.fun;
var newFun2 = newFun.bind(demoObj,5);
newFun2(7,9);//5，7，9