1.function createHeaderSearchLayer中为什么要再定义一次var html="";？外面全局中已经定义过一次了var html=""（第二行）

2.$.ajax中的this（如：done方法中的this）需要var self=this;，不指向Search，指向了谁？为什么？

3.为什么显示隐藏的初始化this.$layer.showHide(this.options);写在autoComplete中？

4.为什么Search.prototype.setInputVal中this.$input.val(removeHTMLTags(value));不需要return？

// JavaScript Document
(function($){
	function Search($elem,options){
		this.$elem=$elem;
		this.options=options;
		this.$input=this.$elem.find('.search-inputbox');
		this.$form=this.$elem.find(".search-form");
		this.$layer=this.$elem.find('.search-layer');
		this.$elem.on("click",".search-btn",$.proxy(this.submit,this));
		if(this.options.autocomplete){this.autoComplete();}
	}
	Search.DEFAULTS={
		autocomplete:false,
		url:"https://suggest.taobao.com/sug?code=utf-8&_ksTS=1581165417160_722&callback=jsonp723&k=1&area=c2c&bucketid=15&q=",
		css3:false,
		js:false,
		animation:"fade"
	};
	Search.prototype.submit=function(){
		if(this.getInputVal()===""){
		   return false;
		   }
		this.$form.submit();
	};
	Search.prototype.autoComplete=function(){
		this.$input
			.on("input",$.proxy(this.getData,this))
			.on("focus",$.proxy(this.showLayer,this))
			.on("click",function(){
				return false;//阻止冒泡，否则$input得到焦点时显示的同时冒泡到document又隐藏了
			});
		this.$layer.showHide(this.options);
		$(document).on("click",$.proxy(this.hideLayer,this));
	};
	Search.prototype.getData=function(){
		var self=this;
		$.ajax({
			url:this.options.url+this.getInputVal(),
			dataType:'jsonp'
		}).done(function(data){
			self.$elem.trigger("search-getData",[data,self.$layer]);
		}).fail(function(){
			self.$elem.trigger("search-noData",[self.$layer]);
		});
	};
	Search.prototype.showLayer=function(){
		if(this.$layer.children().length===0)return;
		this.$layer.showHide("show");
	};
	Search.prototype.hideLayer=function(){
		this.$layer.showHide("hide");
	};
	Search.prototype.getInputVal=function(){
		return $.trim(this.$input.val());
	};
	Search.prototype.setInputVal=function(value){
		this.$input.val(removeHTMLTags(value));
		function removeHTMLTags(str){
			return str.replace(/<(?:[^>'"]|"[^"]*"|'[^']*')*>/g,"");
		}
	};
	$.fn.extend({
		search:function(option,val){
			return this.each(function(){
				var $this=$(this);
				var search=$this.data('search');
				var canshu=$.extend({},Search.DEFAULTS,$this.data(),typeof option==='object'&&option);
				//首先是默认参数，然后是data-active="menu"，最后是传参数时的参数
				if(!search){//如果没有值就进入if判断，添加上实例化的对象；有值的话就不会进入if判断再次实例化了
					$this.data('search',search=new Search($this,canshu));
				}
				//var search=new Dropdown(this,canshu);添加data属性后删除
				//if(typeof option === 'string')这样写不容许出错
				if(typeof search[option]==='function'){
					search[option](val);
				}
			});
		}
	});
})(jQuery);
var $headerSearch=$("#header-search");
var html="",
	maxlength=5;
$headerSearch.on("search-getData",function(e,data,$layer){
	var $this=$(this);
	html=createHeaderSearchLayer(data,maxlength);
	$layer.html(html);
	if(html){
	   $this.search("showLayer");
	   }else{
	   $this.search("hideLayer");
	   }
}).on("search-noData",function(e,$layer){
	$(this).search("hideLayer");
	$layer.html("");
}).on("click",".search-layer-item",function(){
	$headerSearch.search("setInputVal",$(this).html());
	$headerSearch.search("submit");
});
$headerSearch.search({
	autocomplete:true,
	css3:false,
	js:false,
	animation:"fade"
});
function createHeaderSearchLayer(data,maxlength){
	var dataNum=data["result"].length;
	var html="";
	if(dataNum===0){
		//$layer.hide().html("");具体的事情外面解决
		return;
	   }
	for(var i=0;i<dataNum;i++){
		if(i>maxlength)break;
		html+='<li class="search-layer-item text-ellipsis">'+data["result"][i][0]+'</li>';
	}
	return html;
}