Invalid quantifier ? when using Lookbehind regex

[batejo]

Hi,

I'm trying to use in a transformer a regular expression to match some data but I'm getting this error.

Here is an example of what I am doing.

The data:

<value name="VALUE" type="Numeric" unit="Ohm">
     3000
     <escape type="GREATER_THAN_MAX" />
</value>

What I want to match is what is inside the escape.type attribute.

So i execute this javascript in my transformer:

var matches = node.toString().match(/(?<=<escape type=")(.+)(?=" \/>)/);

When deploying my channel I get the error:

SyntaxError: Invalid quantifier ?

How can I use my regular expression without getting the error?

Thanks