javascript画正弦曲线

<div id="context">
    <div id="x-coordinate">
        <div id="x-arrow"></div>
    </div>
    <div id="y-coordinate">
        <div id="y-arrow"></div>
    </div>
</div>    

#context{
    width:500px;
    height:320px;
    margin:150px auto;
    position:relative;
}
#x-coordinate,#y-coordinate{
    position:absolute;
    left:0;
    background-color:#0000FF;
    z-index:1000;
}
#x-coordinate{
    width:500px;
    height:1px;
    top:160px;
}
#x-arrow,#y-arrow{
    width:0px;
    height:0px;
    border:5px solid transparent;
    position:absolute;
}
#x-arrow{
    border-left-color:#0000FF;
    right:-5px;
    top:-5px;
}
#y-arrow{
    border-bottom-color:#0000FF;
    left:-5px;
    top:-5px;
}
#y-coordinate{
    width:1px;
    height:320px;
    top:0;
}
.metaDiv{
    width:1px;
    height:240px;
    border-top:2px solid #0000FF;
}

var metaRadian=(Math.PI*2)/450;
var amplitude=120;
var metaDivs=‘‘;
var context=document.getElementById("context");
for(var i=0,len=450;i<len;i++){
    var top_offset=160-Math.ceil(Math.sin(i*metaRadian)*120);
    metaDivs+="<div class=‘metaDiv‘ style=‘position:absolute;left:"+i+"px;top:"+top_offset+"px‘></div>";
}
context.innerHTML+=metaDivs;