javascript中的replaceAll功能。 

请注意/Microsoft/g，就是这个小g

在本例中，我们将执行一次全局替换，每当 "Microsoft" 被找到，它就被替换为 "W3C"：

<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, "W3C"))

</script>

输出：

Welcome to W3C! We are proud to announce that W3C
has one of the largest Web Developers sites in the world.