<script type="text/javascript">
    console.log( true + 1 );   // 2
    console.log( 'name'+true );  //nametrue
    console.log( undefined + 1 );  //NaN
    console.log( typeof(undefined + 1 ));  //number
    console.log( typeof null );  //Object
    //字符串和其他類(lèi)型相加，變成連接的形式
    
    alert(typeof(NaN));   // number
    alert(typeof(undefined))  // undefined
    alert(typeot(null))  // Object
</script>

console.log( 1 =='1' );     // true
console.log( true == 1 );     // true
console.log( null == undefined );     // true
console.log( [1,2] == '1,2' )   // true

// 考題一：
function c(){
    var b = 1;
    function a(){
        console.log( b  );  // undefined
        var b = 2;
        console.log( b );  //2
    }
    a();
    console.log( b );  // 1
}
c();

// 考題二：
var name = 'World!';
(function(){
	if (typeof name ==='undefined'){
		var name ='Jack':
		console.log('Goodbye'+ name):  // Goodbye Jack
	}else{
		console.log('Hello'+name):
	 }
})()

// 考題三
var bar = 1;
function test(){
	console.log( bar );  //  undefine
	var bar = 2;
	console.log( bar );  // 2
}
test();

function fun( a ){
	var a = 10;
	functibn a(){}
	console.log( a );  // 10
}
fun( 100 );

// 考題四：
function fun(){
    var a = 2;
	function a(){}
		console.log( a );  // 2
}
fun();


function fun(){
	console.log( a );  // f a(){}
	var a = 10;
	function a(){}
}
fun();

function fun(){ // var a
	a=10;
	console.log( a );  // 10
	var a = 20;
	console.log( a );  // 20
}
fun();

// 面試題一：
console.log( [1,2,3] === [1,2,3] );  // true

// 面試題二：
var obj1= {
	a：'hellow‘
}
var obj2 = obj1
obj2.a = 'world'
console.log(obj1)	//{a:'world'}
(function(){	
	console.log(a)  // undefinud
	var a=1
})();

// 面試題三：
var a = {};
var b = {
	key:'a'
}
var с = {
	key:'c"
}
a[b] ='123';
a[c] ='456';
console.log( a[b] )  // '456'

// 考題一：
function Foo({
	getName= function(){console.log(1)}//注意是全局的window.
	return this;
}

Foo.getName = function()(console.log(2))
Foo.prototype.getName = function()(console.log(3)}
var getName = function()(console.log(4))
function getName(){
	console.log(5)
}

Foo.getName();	 // 2
getName();	  // 4
Foo().getName(); // 1
getName();   // 1
new Foo().getName();   // 3

// 考題二：
var o ={
	a:10,
	b:{
		fn:function(){
			console.log(this.a );	// undefined
			console.log(this)	  // {fn:f}, 代表對(duì)象
		}
	}
}
o.b.fn();

方法一：isArray
var arr = [1,2,3];
console.log(Array isArray( arr ) );

方法二：instancerof
var arr = [1,2,3];
console.log( arr instanceof Array);

方法三：原型prototype
console.log( Object.prototype.toString.call(arr).indexOf('Array') > -1):

方法四：isPrototypeOf()
console.log( Array.prototype.isPrototypeof(arr))

方法無(wú)：constructor
console.log( arr.constructor.toString().indexof('Array') > -1）

方式一：new Set
var arr1 = [1,2,3,2,4,1];
console.log( Array.from( new Set(arr1)));  // [1,2,3,4]
console.log( [...new Set(arr1)] );  // [1,2,3,4]

function unique(arr){
	return [...new Set(arr)]
}
console.log(unique(arr1) );  // [1,2,3,4]

方式二：indexOf
var arr2 = [1,2,3,2,4,1];
function unique( arr ){
	var brr = [];
	for( var i=0;i<arr.length;i++){
		if( brr.indexOf(arr[i]) == -1){
			brr.push( arr[i] );
		}
	}
	return brr;
}
console.log( unique(arr2) );  // [1,2,3,4]

方式三：sort
var arr3 = [1,2,3,2,4,1];
function unique( arr ){
	arr = arr.sort();
	var brr = [];
	for(var i=0;i<arr.length;i++){
		if(arr[i] !== arr[i-1]){
		brr.push( arr[i] );
		}
	}
	return brr;
}
console.log( unique(arr3) );  // [1,2,3,4]

function fnArr(arr){
	var newArr = [];
    
	arr.forEach((item,index)=>{
		newArr.push(Math.max(...item))
	})
	return newArr;  // [5, 27, 39, 1001]
}
console.log(fnArr([
	[4,5,1,3],
	[13,27,18,26],
	[32,35,37,39],
	[1000,1001,857,1]
]))

/*考題：
1.給字符串對(duì)象定義一個(gè)addPrefix函數(shù)，當(dāng)傳入一個(gè)字符串str時(shí)，它會(huì)返回新的帶有指定前
綴的字符串，例如：
console.log("world".addPrefix("hello")
控制臺(tái)會(huì)輸出:：“helloworld"
*/
String.prototype.addPrefix = function(str){
	return str + this;
}
console.log('world'.addPrefix('hello'))  // helloworld

var str = 'helloworld'
var obj={};
for(var i=0;i<str.length;i++){
    //charAt() 方法可返回指定位置的字符。
	var char = str.charAt(i);
	if( obj[char]){
		obj[char]++;
	}else{
		obj[char] = 1;
    }
}
console.log( obj );  // {h: 1, e: 1, l: 3, o: 2, w: 1, …}

//統(tǒng)計(jì)出來(lái)最大值
var max = 0;
for( var key in obj ){
	if( max < obj[key] ){
		max = obj [key];
    }
}
//拿最大值去對(duì)比
for( var key in obj ){
	if(obj[key] == max ){
		console.log('最多的字符是' + key);  //最多的字符是l
		console.log('出現(xiàn)的次數(shù)是' + max);  // 出現(xiàn)的次數(shù)是3
    }
}

// 方法一：ES6
class Parent{
	constructor(){
		this.age = 18;
	}
}
class Child extends Parent{
	constructor({
		super();
		this.name ='張三';
	}
}
let o1 = new Child();
console.log( o1,o1.name,o1.age );

//方法二：原型鏈繼承（實(shí)現(xiàn)了共享）
function Parent(){
	this.age = 20;
}
function Child(){
	this.name= '張三'
}

Child.prototype = new Parent();
let o2 = new Child();
console.log( o2,o2.name,o2.age ); // {name:'張三',age:20},'張三'，20

// 方法三：借用構(gòu)造函數(shù)（實(shí)現(xiàn)不了共享）
function Parent(){
	this.age = 20;
}
function Child(){
    Parent.call(this);
	this.name= '張三';
}

let o3 = new Child();
console.log( o3,o3.name,o3.age ); // {name:'張三',age:20} '張三' 20

// 方法四：組合式繼承（既可以實(shí)現(xiàn)共享，也可以解決原型鏈問(wèn)題）
function Parent(){
	this.age = 20;
}
function Child(){
    Parent.call(this);
	this.name= '張三';
}

Child.prototype = new Parent();
let o4 = new Child();
console.log( o4,o4.name,o4.age ); // {name:'張三',age:20} '張三' 20

var str='你好';
varobj={str:'這是obj對(duì)象內(nèi)的str'}
function fun(){
	console.log( this, this.str );
}
//fun.call（obj）; // call立即執(zhí)行
//fun.apply(obj）; // apply立即執(zhí)行
fun.bind(obj)(); // 執(zhí)行結(jié)果為函數(shù)
fun. bind(obj) ; // bind不會(huì)立即執(zhí)行，因?yàn)閎ind返回的是函數(shù)

fun();
var str ='你好';
varobj={str:'這是obj對(duì)象內(nèi)的str'}
function fun( name, age ){
	this.name = name;
	this.age = age;
	console.log( this,this.str );
}
fun.call(obj,‘張三',18); // {str:'這是obj對(duì)象內(nèi)的str'，name：'張三',age:18} '這是obj對(duì)象內(nèi)的str'
fun.apply(obj,['張三',88]);// {str:'這是obj對(duì)象內(nèi)的str'，name：'張三',age:88} '這是obj對(duì)象內(nèi)的str'
fun.bind(obj,['張三',88])();// {str:'這是obj對(duì)象內(nèi)的str'，name：['張三',88],age:undefined} '這是obj對(duì)象內(nèi)的str'
fun.bind(obj,'張三',88)();// {str:'這是obj對(duì)象內(nèi)的str'，name：'張三',age:88} '這是obj對(duì)象內(nèi)的str'

// apply
var arr1= [1,2,4,5,7,3,321];
console.log(Math.max.apply(null,arr1))

// bind
var btn = document.getElementById('btn');
var h1s = document.getElementById('h1s');
btn.onclick = function(){
	console.log( this.id );
}.bind(h1s)

var arr1= [12,11,1,23,'45','34',21,'b','a','ab','bc'];
console.log( arrl.sort());  // [1,11,12,21,23,'34'，'45','a','ab'，'b'，'bc']

var arr2= [12,111,11,1,23,'45','34',21];
var arr3 = arr2.sort(function( a, b ){
	return b-a;
})
console.log( arr3 );  // [111,'45','34',23,21,12,11,1]
var arr4 = [
	{name:'zhangsan',age:18},
	{name:'lisi',age:2},
	{name:'wangwu',age:50},
];

function compare(age){
	return function(a,b){
		var val1 = alage];
		var val2 = b[age];
		return val1 - val2;
    }
}

var arr5 = arr4.sort(compare('age'));

console.log( arr5 );//  {name:'wangwu',age: 50}
					//	{name:'zhangsan',age: 18}
					//  {Rname:'lisi',age:2} 

// 1、淺拷貝
var arr1= ['a','b','c','d'];
var arr2 = arr1;
arr1[0]='你好嗎';
arr2[1]='還行';
console.log( arr1, arr2 ); // ['你好嗎'，‘還行','c','d']

var obj1 = {a:1,b:2}
var obj2 = Object.assign(obj1);
obj1.a = '100';
obj2.b = '你怎么養(yǎng)';
console.log( obj1,obj2); // {a:'100',b:'你怎么養(yǎng)'}

// 2、深拷貝
var obj3 = {
	a:1,
	b:2
}
var obj4 = JSON.parse(JSON.stringify( obj3));
obj3.a = '100′;
obj4.b = '你怎么陽(yáng)' 
console.log( obj3, obj4 ); // {a: '100'，b:2}{a:1,b:'你怎么陽(yáng)'}

// 遞歸形式
var obj5 ={
	a:1,
	b:2,
	arr:['a','b','c','d']
}
function copyObj( obj ){
	if（Array.isArray(obj){
		var newObj = [];
	}else{
        var newObj = {};
    }
	for( var key in obj ){
		if( typeof obj[keyl =object' ){
			newObj[key] = copyObj(obj[keyl);
		}else{
			newObj[key] = obj[key];
        }
    }
	return newObj;
}
console.log(copyObj(obj5));