javascript中replace的使用方法其实还是有很多种的，这里先讲一下常规替换的使用方法。
javascript中replace默认替换是只替换找到的第一个类似的匹配字段，如下：
<script type="text/javascript">
var str="Visit Microsoft!"
document.write(str.replace(/Microsoft/, "W3School"))
</script>输出效果如下：
Visit W3School!
要想全部替换则需要使用正则表达式来完成，如下：
<script type="text/javascript">
var str="Welcome to Microsoft! "
str=str + "We are proud to announce that Microsoft has "
str=str + "one of the largest Web Developers sites in the world."
document.write(str.replace(/Microsoft/g, "W3School"))
</script>输出效果如下：
Welcome to W3School! We are proud to announce that W3School has one of the largest Web Developers sites in the world.