Check if string is a prefix of a Javascript RegExp

Question

In Javascript I have defined a regular expression and now a user is typing in a string. I want to tell him if his string still could match the RegExp if he continues typing

Answer 1

One way of doing this could be to hook to the onKeyUp event of a text box and .test the text against the regular expression. My assumption is of course that you want to do a regular expression matching. I'm not sure if this is exactly what you need, in fact your code:

"a".isPrefixOf( re ); // true

will never match since it's required to also have a subsequent "b" character (you may want to modify the regular expression). For instance, this code will test against any string matching this format:

a-n(n)-b

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