js点击图片显示在左边大图

<div class="imgbox cf">
    <img src="temp/pic2.jpg" alt="" class="big_pic" id="big_pic">
    <div class="sm_img" id="sm_img">
        <img src="temp/pic2.jpg" alt="" onmouseover="document.getElementById('big_pic').src='temp/pic2.jpg'">
        <img src="temp/pic1.jpg" alt="" onmouseover="document.getElementById('big_pic').src='temp/pic1.jpg'">
        <img src="temp/pic2.jpg" alt="" onmouseover="document.getElementById('big_pic').src='temp/pic2.jpg'">
        <img src="temp/pic1.jpg" alt="" onmouseover="document.getElementById('big_pic').src='temp/pic1.jpg'">
        <img src="temp/pic2.jpg" alt="" onmouseover="document.getElementById('big_pic').src='temp/pic2.jpg'">
        <img src="temp/pic1.jpg" alt="" onmouseover="document.getElementById('big_pic').src='temp/pic1.jpg'">
        <img src="temp/pic2.jpg" alt="" onmouseover="document.getElementById('big_pic').src='temp/pic2.jpg'">
        <img src="temp/pic1.jpg" alt="" onmouseover="document.getElementById('big_pic').src='temp/pic1.jpg'">
        <img src="temp/pic2.jpg" alt="" onmouseover="document.getElementById('big_pic').src='temp/pic2.jpg'">
    </div>
</div>