fixie

Fix elements vertically as the page scrolls down. Configurable, reusable. "Pin" the given element to the top of the page on vertical scroll. Also know as "conditional fixed placement".

No dependencies. Useful if you're not using React or something like that.

The main feature is that this supports different strategies. All the code I saw took a single approach, and it may not work for your markup or page length. This tool allows you to try different techniques, or event switch in different situations.

If you're looking for the jQuery plugin, use an earlier, < 2.0 version. The current one does not require jQuery. (There's no reason it won't work at the same time, though.)

If you want jQuery (or some other feature), let me know. I think I'm the only one using this, so I am not implementing backward compatibility unless asked.

Demo

> git clone ...
> yarn install
> open demo.html

http://ndpsoftware.com/fixie/demo.html

Usage

Webpack or similar

> yarn add fixiejs

  // my-file.js
  import { fixie } from 'fixiejs'
  const el = document.getElementById(...) or $('#menu')[0]
  fixie(el);   // use defaults
  fixie(el, { topMargin: '20px' }); // see Options below

Direct inclusion on web pages

This is not recommended, but if you want, dist/fixie.min.js can be directly included on a web page. Just grab it, similar to how the demo page does.

Options

Accepts an options object, which may contain (with defaults):

• strategy: fixed Choose an implementation. See below.
• topMargin: 0 Specifies how close to the top to pin the element. Usually you want elements pinned to the top, but sometimes they need to be below some other element, such as a fixed header.
• pinnedClass: _pinnedToTop Any css class to add on to the element when it is pinned.
• pinnedBodyClass: undefined A CSS class to add to the body element when this element is pinned. Default is to add no class.
• throttle: 30 (ms) How often to adjust position of element
• pinSlop: 0 Usually when the user scrolls an element to the top of the page, it becomes "fixed". This "slop" value allows it to go past, or become fixed before it's actually at the top.

Strategies

There are various strategies available:

• relative: simply make the element positioned relative and adjust position whenever the user scrolls. Works with simple elements
• relativeWithHiding: same as above, except fades out and shows elements as they move
• fixed: makes the element fixed positioned. This is very performant, but it has a couple drawbacks. First, you must take care that when the element becomes "fixed", that it maintains its natural width. This is better done with your CSS than fixie itself, so that the pinned element can respond well to browser resizing. Often this is only a "width: 100%" statement.

Development

Uses minimal tooling. See package.json for relevant stuff.

Rollup is used to build minified web-ready file, but otherwise not needed.

License

Copyright (c) 2013-2021 NDP Software. Andrew J. Peterson MIT License; see LICENSE.txt

History

• 2021-07-29 Convert to Typescript
• Bug fix: relativeWithHiding strategy resets opacity to inherit after element is made visible, so that fixed items can have any opacity applied with CSS.
• 1.0.1: add bower file
• 1.0.0: first release

References

• http://github.com/ndp/jsutils for tests
• http://www.gregjopa.com/2011/07/conditional-fixed-positioning-with-jquery/