Better imenu to show functions and data

Hi,
Currently the imenu shows some html tags. I'd like it to show javascript functions, and possibly different sub-menus for computed properties or methods.

I tried something but it is unclear to me how to add regular imenu entries.

I have a regexp, checked with the regexp-builder:

(setq imenu-generic-expression
'(("methods" "^\\s-*\\([a-zA-Z0-9_]+\\): function" 1)))

I don't know how to override the existing entries and use just that. I tried:

(add-hook 'vue-mode-hook
(lambda ()
(set (make-local-variable imenu-generic-expression)
'(("methods" "^\\s-*\\([a-zA-Z0-9_]+\\): function" 1))
)))

as discussed on emacswiki and [SE](https://emacs.stackexchange.com/questions/10105/imenu-generic-regexp-for-css-less) and as seen in a couple of other packages, with no luck.

An example file:

```
data: function() {
return {
page: 1,
};
},

props: {
title: String,
url: String,
},

computed: {
entries() {
log("hello");
},

methods: {
previousPage: function () {
// ...
},

```
there would be functions and data to catch, hence a few imenu regexps to write.

Any ideas ?

imenu doc: https://www.gnu.org/software/emacs/manual/html_node/elisp/Imenu.html

**edit**: I tried what you can see in the following commit.

The payload names imenu-generic-expression and vue-mode-hook as the relevant entry points; start with those and the linked Emacs Imenu documentation, then inspect how vue-mode currently supplies HTML entries. Done means the imenu presents JavaScript functions and data, with suitable submenus for computed properties or methods, without the existing unwanted entries.

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