What would be a regular expression which I can use to match a valid JavaScript function name...
E.g. myfunction would be valid but my<fun>ction would be invalid.
[a-zA-Z0-9_])?
[EDIT] See @bobince's post below for a more correct and thorough answer. This answer has been retained for reference and edited to be less wrong.
A valid name in JavaScript must start with a Unicode letter (p{L}), dollar sign, or underscore then can contain any of those characters as well as numbers, combining diacritical (accent) characters, and various joiner punctuation and zero-width spaces. Additionally, it cannot be a word reserved by the JavaScript language (e.g. abstract, as, boolean, break, byte, case, etc).
A full regular expression solution would be quite complicated in plain JavaScript but the XRegExp Unicode plugin could greatly simplify the task. This online function name tester might also be useful.
[ORIGINAL] Here is an incomplete regular expression, using only the US ASCII letters:
var fnNameRegex = /^[$A-Z_][0-9A-Z_$]*$/i;
You also must check that it doesn't match any reserved words (e.g. abstract, boolean, break, byte, ..., while, with, etc). Here's a start for that list, and an example function:
var isValidFunctionName = function() {
var validName = /^[$A-Z_][0-9A-Z_$]*$/i;
var reserved = {
'abstract':true,
'boolean':true,
// ...
'with':true
};
return function(s) {
// Ensure a valid name and not reserved.
return validName.test(s) && !reserved[s];
};
}();
