javascript regex backrefence

Question

This is the continuation of php regex: phone number 7-12 digits may contain hypen or space

I'm still trying to understand backreferences. The following is the JavaScript code I came up with to test backreferences. When I run this code only null is being outputted. Where am I going wrong?

<script type="text/javascript">
function myRegexFunc()
{   myString="abcabcxabcdefghi";
    patt1=new RegExp("(abc)?\1x\1");
    document.write(patt1.exec(myString));
}
</script>
</head>

<body onload="myRegexFunc()">
</body>

score 3 · Answer 1 · answered Oct 05 '12 at 10:35

3

You need to escape the \ in the string.

patt1 = new RegExp("(abc)?\\1x\\1");

Or you could use the regex literal:

patt1 = /(abc)?\1x\1/;

answered Oct 05 '12 at 10:35

xdazz

158,678
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Can you tell why why there is a comma followed by "abc"? I thought the result should only be "abcabccxabc". Thank you. – vaanipala Oct 05 '12 at 16:36
@vaanipala because the result is an array. – xdazz Oct 05 '12 at 21:56
But there should only be one match for this. I still don't understand about the second "abc" in the output. Please help. – vaanipala Oct 08 '12 at 07:15

javascript regex backrefence

1 Answers1