marc walter

New major version of folder-hash (2.0)


A while ago I released a library that creates checksums over folders and files for node.js.
Now I prepared a new major version, which adds the possibility to specify more sophisticated include and exclude rules. I also added CircleCI configuration build

Example usage:

const { hashElement } = require('folder-hash');

const options = {
    folders: { exclude: ['.*', 'node_modules', 'test_coverage'] },
    files: { include: ['*.js', '*.json'] }

console.log('Creating a hash over the current folder:');
hashElement('.', options)
    .then(hash => {
    .catch(error => {
        console.error('hashing failed: ', error);
read more

Mouse scroll events in Elm (using JSON decoders)

2018-03-29 (Last updated on 2018-09-01)

Handling scroll events in Elm is not perfect, but on the elm discourse channel the user @ilias pointed out a nice way:

In Elm 0.18 and 0.19:

Use a port to send wheel events from JavaScript to the Elm app

const app = Elm.Main.init({ node: document.querySelector('main') })
document.addEventListener("wheel", app.ports.onWheel.send);

and decode them into an Elm Msg type

type Msg
    = NoOp
    | Wheel { deltaX : Float, deltaY : Float }

port onWheel : (Json.Decode.Value -> msg) -> Sub msg

subscriptions : model -> Sub Msg
subscriptions _ =
    onWheel Wheel
        (\val ->
            case Decode.decodeValue wheelDecoder val of
                Ok model ->
                    Wheel model

                Err _ ->

wheelDecoder : Json.Decoder Model
wheelDecoder =
    Json.Decode.map2 Model
        (Json.Decode.field "deltaX" Decode.float)
        (Json.Decode.field "deltaY" Decode.float)


In the future

Remove the port, and use the new onWindow or onDocument functions:

subscriptions : model -> Sub Msg
subscriptions _ =
    onDocument "wheel" ( Wheel wheelDecoder)

This was proposed for Elm 0.19, but unfortunately it did not make it into the final release.

read more

Elm Filedrop example

2018-02-11 (Last updated on 2018-09-01)

A simple example that uses the HTML Drag&Drop API to generate dataURI strings when dropping files onto an HTML element.


This is a good example to show how it is possible to use Browser APIs that are not available to elm. Elm does not support the file list that is emitted in the drop event, but when passing the event data through a port to JavaScript code it is still possible to use the API.
No need to listen to the API events in JS, just use elm and pass the result.

read more

Focusing elements in Elm

2018-01-31 (Last updated on 2018-09-01)

A reminder how to focus input elements using Elm without I want to add elements to a list and automatically focus on them.

A nice solution on stackoverflow from robertjlooby is this:

The focus function in the elm-lang/dom package is used to set focus with a Task (without using any ports or JavaScript).

Internally it uses requestAnimationFrame to ensure any new DOM updates are rendered before it tries to find the DOM node to focus on.

type Msg
    = FocusOn String
    | FocusResult (Result Dom.Error ())

update : Msg -> Model -> ( Model, Cmd Msg )
update msg model =
    case msg of
        FocusOn id ->
            ( model, Dom.focus id |> Task.attempt FocusResult )

        FocusResult result ->
            -- handle success or failure here
            case result of
                Err (Dom.NotFound id) ->
                    -- unable to find dom 'id'
                Ok () ->
                    -- successfully focus the dom

He also created a fully working ellie example for Elm 0.18, which I converted to Elm 0.19.

read more

Decoding models from a JSON formatted string

2018-01-17 (Last updated on 2018-09-01)

A small snippet useful if one Elm program consists of two very different components.

How to use it:

  1. Pass data to the instantiation of the elm program as a String
  2. Try different decoders on the data (Json.Decode.oneOf)
  3. Display the SPA that can handle the data or an error page

If this iframe is not displayed, try opening the file directly.

read more

Cross-browser copy-to-clipboard support


Recently I needed to add a copy-to-clipboard functionality to a project. Usually, clipboard.js is an awesome tool to add support for it with great browser support and nice fallback handling for unsupported browsers.

Because the program is written in elm I wanted to keep the number of JavaScript dependencies to a minimum and decided to write this code on my own.

Result is this JsBin. For my purposes it worked well, I only need support for the current versions of the major desktop browsers (Firefox, Chrome, Edge and Safari) and on iOS 11.

Just like clipboard.js I used the Selection and ExecCommand APIs. Fallback mechanisms were not needed for my use case.

read more

Mini game 1 + 2 = 3

2017-10-08 (Last updated on 2018-09-01)

I saw a nice little example game written by Emanuele Feronato where you need to calculate sums and differences using only 1, 2 or 3.

I then decided to program it using elm.

You can use either mouse, fingers, or the keyboard to enter the correct values and try to get as high a score as possible. The highscore is saved to local storage.

If this iframe is not displayed, try the game directly.

read more

Using Prism with marked for static syntax highlighting


This content is built from markdown files to static html. Syntax highlighting for code snippets is also generated during this step. It is very easy to add syntax-highlighting only in the browser, but I wanted to remove the necessary JavaScript dependencies from the HTML code and the additional rendering effort for the browser.


let ab = { cde: 1, fg: 'h' }
console.log(`Variable ab = ${ab}`)

// comment
ab.i = 17
read more

CSS styles in elm-reactor and pretty check boxes

2017-08-16 (Last updated on 2018-09-01)

Elm-reactor is a great tool to get started in elm.
It supports a time-traveling debugger, downloads the necessary packages and is generally nice to work with.

A problem though is that for styling you usually need to write inline-styles. This is sometimes fine, but if I want to concentrate on the elm code and add separate styles I usually pick another tool like create-elm-app.

But it is possible to add a style tag to the main view function and the css styles are applied to the document.
After the initial exploration, I can move the styles to a dedicated file.

If this iframe is not displayed, open the file directly.

This uses checkboxes I adapted from a really nice example by @valerypatorius on codepen.

The trick

Render a style node and specify the content as a multiline string.

module Main exposing (main)

import Html exposing (Html, div, h1, text)
import Html.Attributes exposing (class)

main =
    div []
        [ Html.node "style" [] [ text css ]
        , h1 [] [ text "Example" ]

css =
    """/* injected css */
html {
    background-color: #f0c;
    color: #fff!important;


read more

Feedback form with mail in PHP


A simple form that I used to receive feedback from people on a web page. The web app uses JavaScript and only works on current browsers. I receive feedback if JavaScript is executed in the user's browser and the UserAgent of the browser (browser and operating system name and version).

This snippet only needs one file to both display the form and to receive the information.
Also needed is a configured mail server to send this information to me and the user (if she wishes it).

read more