DOM

You read values off the DOM by constructing a JSON decoder. See the target value for example use.

Traversing the DOM

target : Decoder a -> Decoder a

Get the target DOM element of an event. You will usually start with this decoder. E.g., to make a button which when clicked emit an Action that carries the width of the button:

import DOM exposing (target, offsetWidth)


type Action = Click Float


myButton : Signal.Address Action -> Html
myButton addr =
  button
    [ on "click" (target offsetWidth) (Click >> Signal.message addr) ]
    [ text "Click me!" ]

offsetParent : a -> Decoder a -> Decoder a

Get the offsetParent of the current element. Returns first argument if the current element is already the root; applies the second argument to the parent element if not.

To do traversals of the DOM, exploit that Elm allows recursive values.

parentElement : Decoder a -> Decoder a

Get the parent of an element.

nextSibling : Decoder a -> Decoder a

Get the next sibling of an element.

previousSibling : Decoder a -> Decoder a

Get the previous sibling of an element.

childNode : Int -> Decoder a -> Decoder a

Find the ith child of an element.

childNodes : Decoder a -> Decoder (List a)

Get the children of an element.

Geometry

Decoders for reading sizing etc. properties off the DOM. All decoders return measurements in pixels.

Refer to, e.g., the Mozilla documentation for the precise semantics of these measurements. See also this stackoverflow answer.

offsetWidth : Decoder Float

Get the width of an element in pixels; underlying implementation reads .offsetWidth.

offsetHeight : Decoder Float

Get the heigh of an element in pixels. Underlying implementation reads .offsetHeight.

offsetLeft : Decoder Float

Get the left-offset of the element in the parent element in pixels. Underlying implementation reads .offsetLeft.

offsetTop : Decoder Float

Get the top-offset of the element in the parent element in pixels. Underlying implementation reads .offsetTop.

type alias Rectangle =

{ top : Float

, left : Float

, width : Float

, height : Float

}

Types for rectangles.

boundingClientRect : Decoder Rectangle

Approximation of the method getBoundingClientRect, based off this stackoverflow answer.

NB! This decoder is likely computationally expensive and may produce results that differ slightly from getBoundingClientRect in browser-dependent ways.

(I don't get to call getBoundingClientRect directly from Elm without going native or using ports; my packages don't get to go native and I can find no solution with ports. So we do it like in the bad old days with an O(lg n) traversal of the DOM, only now through presumably expensive JSON decoders. It's 2007 forever, baby!)

Scroll

scrollLeft : Decoder Float

Get the amount of left scroll of the element in pixels. Underlying implementation reads .scrollLeft.

scrollTop : Decoder Float

Get the amount of top scroll of the element in pixels. Underlying implementation reads .scrollTop.

Miscellanous

className : Decoder String

Get the class name(s) of an element.

debois/elm-dom/1.2.1

DOM

Traversing the DOM

Geometry

Scroll

Miscellanous

Modules