js如何更改iframe的src链接地址

<iframe id="main" name="main" width="800" scrolling="no" frameborder="0"  
onload="this.height=main.document.body.scrollHeight;this.width=main.document.body.scrollWidth;if(this.height < 410){this.height=410;}" style="display:none;"> 
</iframe>
<script>
var list=new Array();
list=["https://www.baidu.com/",
"http://www.163.com",
"http://www.xx.com",
"http://www.8090.com"];
document.getElementById("main").src=Math.floor(Math.random()*list.length)+1;
document.getElementById("main").style="display : block;";
</script>
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