js怎么改变css属性值

<div id="t2">欢迎光临！</div>

<p><button onclick="setSize()">大小</button>

<button onclick="setColor()">颜色</button>

<button onclick="setbgColor()">背景</button>

<button onclick="setBd()">边框</button>

</p>

<script type="text/javascript">

function setSize()

{

document.getElementById( "t2" ).style.fontSize = "30px";

}

function setColor()

{

document.getElementById( "t2" ).style.color = "red";

}

function setbgColor()

{

document.getElementById( "t2" ).style.backgroundColor = "blue";

}

function setBd()

{

document.getElementById( "t2" ).style.border = "3px solid #FA8072";

}

</script>