html中调用js文件中的广告代码调用方式

示例：html代码如下

<script src="/js/ceshi.js" type="text/javascript"></script>
<div class="ad1"><script>img1();</script></div>
<div class="ad2"><script>img2();</script></div>
<div class="ad3"><script>img3();</script></div>
<div id="ad1"></div>
<div id="ad2"></div>
<div id="ad3"></div>

js文件中的代码如下：

function img1() {
    document.write("<p>1</p>");
}

function img2() {
    document.write("<p>2</p>");
}

function img3() {
    document.write("<p>3</p>");
}


window.onload = function() {
    document.getElementById("ad1").innerHTML = "<p>1</p>";
    document.getElementById("ad2").innerHTML = "<p>2</p>";
    document.getElementById("ad3").innerHTML = "<p>3</p>";
}