代码编辑器：
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<meta charset="utf-8">3
<title>正则表达式 | 简单教程 ( www.twle.cn )</title>4
<script>5
var str = "Is is the cost of of gasoline going up up";6
var patt1 = /\b([a-z]+) \1\b/ig;7
document.write(str.match(patt1));8
</script>9
<meta charset="utf-8"><title>正则表达式 | 简单教程 ( www.twle.cn )</title><script>var str = "Is is the cost of of gasoline going up up";var patt1 = /\b([a-z]+) \1\b/ig;document.write(str.match(patt1));</script>