activity-listener/README.md

Respond to ui-events before or after ordinary event-handlers do

# Activity Listener

Respond to ui-events before or after ordinary event-handlers do.

Usage:
* address obscure tasks:
    blur elements after clicking when peripherals emit enter-keys.

Bad usage:
* cross-tab interaction:
    use localstorage-events or serviceworker messaging
* record user activity:
    you want the [Inactivity Listener](https://www.npmjs.com/package/inactivity-listener)
    for that.

But I can code that myself!
Sure, but this module knows the tricks and can be controlled from different places!

## Install

Install the package as npm package. Provided are
a umd-formatted file in the dist folder to require or just read
and an es-module in the module folder to import.

## Usage

To register calls at the very start an event:
```js
const logoff = function () {
    if (!localStorage.authToken && user.name) {
        loginService.logoff()
    }
}
const eraseClickLogoff = activityListener.register('click', logoff)
```

To register calls at the end of an event's propagation:
```js
const blur = function () {
    const focussed = document.querySelector('*:focus')
    if (focussed) {
        focussed.blur()
    }
}
const eraseClickBlur = activityListener.register('click', undefined, blur)
```

Or to register calls both at the start and the end,
and allow time for the handlers to finish:
```js
const eraseClickRegistration = activityListener.register('click', logoff, blur, 100)
```

To undo the registration:
```js
activityListener.erase('click', logoff)
activityListener.destroy() // erase all
eraseClickRegistration()
```
note that 'clear' is now deprecated

flow methods:
```js
activityListener.pause()
activityListener.resume()
```

## Demo

.../activity-listener/demo/activityListener.html