Install

npm i @yaireo/position -S

UMD file link:

https://unpkg.com/@yaireo/position

Example

import position from '@yaireo/position'

position({
  // the element wished to be positioned in a certain place
  target: targetElement,

  // reference DOM element or an Object like so: {x:10, y:20}
  ref: refElement,

  // [optional] default target plaement string, relative to the ref
  // first string value is horizontal and then vertical placement. Examples:
  // 'left center', 'right below', 'center center'
  placement:'center above',

  // [optional] distance from reference element
  offset: [20],

  // [optional] by default the positioning updates within a RequestAnimationFrame callback,
  //but this can cause painting delays when resizing or scrolling fast.
  useRaf: false,
})

This scripts places an element next to another element (at a certain prefered relative place). If you want to update the targer's position (relativce to the referece) when the page scrolls or resizes I advice adding observers:

const observerCallback = () => position({ target:targetElement, ref:refElement })

// create observers instances
const resizeObserver = new ResizeObserver(observerCallback)
const intersectionObserver = new IntersectionObserver(observerCallback, {root:document, threshold:1})

// start observing (using the instances created above)
resizeObserver.observe(document.body)
intersectionObserver.observe(targetElement)

CSS

This script adds CSS variables (custom properties) on the target element:

| CSS Variable | | ------------------- | | pos-left | | pos-top | | pos-target-width | | pos-target-height | | pos-ref-width | | pos-ref-height | | pos-ref-left | | pos-ref-top | | window-scroll-y | | window-scroll-x' |

Using the above mix of variables, write this CSS in your code to position the target:

[positioned]{
  --x: calc(var(--pos-left) + var(--window-scroll-x));
  --y: calc(var(--pos-top) + var(--window-scroll-y));
  position: absolute;
  z-index: 999999;
  top: 0;
  left: 0;
  transform: translate(calc(var(--x) * 1px),
                       calc(var(--y) * 1px));
}