我如何创建像Facebook或WhatsApp这样的搜索框?(移动)

var searchbox={
	topPos_open:0, topPos_close:-50, isOpen:false,
	open:function(){
	    var box=document.getElementById("searchbox");
	    box.style.top=this.topPos_open+"px";
        document.getElementById("searchfield").focus();
        this.isOpen=true;
	},
	close:function(){
	    var box=document.getElementById("searchbox");
	    box.style.top=this.topPos_close+"px";
	    this.isOpen=false;
	},
	pop:function(){
	    !this.isOpen?this.open():this.close();
	},
	clear:function(){
		document.getElementById("searchfield").value="";
	}
}

#searchbox{position:fixed; top:-50px; left:0px; width:100%; height:60px; background-color:rgba(135, 206, 235, 1); -webkit-transition:top 0.5s ease 0s; -moz-transition:top 0.5s ease 0s; transition:top 0.5s ease 0s;}
#searchbox input{border:0px none; margin:0px 10px 0px 10px; padding:0px; width:80%; font-size:20px;}
#searchbox #input{float:left; background-color:rgba(255, 255, 255, 1); border:1px solid #dddddd; border-radius:20px; margin:5px; padding:5px; width:70%; min-width:250px;}
#searchbox #close{float:right; padding:10px:}
#searchbox button{border:0px none; background-color:transparent; font-size:20px; cursor:pointer;}
#searchbox #dots{clear:both; text-align:center; font-size:25px; cursor:pointer;}

<div id="searchbox">
    <div id="input">
      <input type="text" id="searchfield" value="">
      <button type="button" onclick="searchbox.clear()">
        X
      </button>
    </div>
    <div id="close">
      <button type="button" onclick="searchbox.close()">
        Cancel
      </button></div>
    <div id="dots" onclick="searchbox.pop()">
      ......
    </div>
</div>


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Click the dots