vh-check

get reliable CSS vh sizes for 1kb gzipped

• the problem
• why not use viewport-units-buggyfill?
• use
  • as a global variable
  • as a commonJS module
  • as a ES module module
  • how it works
  • returned object
• example
  • in your javascript
  • in your CSS
• configuration
  • as a string
  • as an object
    • cssVarName
    • force
    • bind
    • redefineVh
    • updateOnTouch
    • onUpdate
• about browser support
• demo
  • github pages
  • local
• caveats
• other stuff
  • changelog
  • migrating
  • run the tests
  • thanks
  • related

the problem

Browsers don't always compute the vh unit the same way. Some mobile browsers compute the vh CSS unit without taking care of the url bar. That means that a 100vh div will overflow the viewport by the size of the url bar.

This is the current behavior for:

• Safari iOS
• Chrome android >= 56

As explained in the chrome post, that make sense but make it hard to have a full hero top block.

This script will measure the difference and put it in a CSS var. You can read more on this css-trick article by Louis Hoebregts

why not use viewport-units-buggyfill?

It's doing a very good job:

https://github.com/rodneyrehm/viewport-units-buggyfill

But it has some problems with media-queries:

https://github.com/rodneyrehm/viewport-units-buggyfill/issues/13

use

as a global variable

<script src="https://unpkg.com/vh-check/dist/vh-check.min.js"></script>
<script>
  (function () {
    // initialize the test
    var test = vhCheck();
  }());
</script>

as a commonJS module

npm install vh-check

var check = require('vh-check')
var test = vhCheck() // return an object (see below)

as a ES module module

npm install vh-check

import vhCheck from 'vh-check'
const test = vhCheck()

how it works

• It will update the vh-check CSS custom property if needed
• vh-check will be updated on orientationchange event
• vh-check will not be updated on scroll event by default

returned object

vh-check will return a full object:

{
  isNeeded: false,
  // wether or not it's needed
  value: 0,
  // the CSS var value
  vh: 480,
  // a 100vh div size
  windowHeight: 480,
  // same value as window.innerHeight
  offset: 0,
  // difference between the above sizes
  recompute: function computeDifference(),
  // call this to programmatically get all the values and set the CSS var
  // - this can be useful if you want to add your own listeners
  //   that will trigger a computation
  unbind: function unbindVhCheckListeners(),
  // call this to remove any window listeners created by vh-check
},

example

in your javascript

vhCheck()

in your CSS

main {
  height: 100vh;
  /* If you need to support browser without CSS var support (<= IE11) */
  height: calc(100vh - var(--vh-offset, 0px));
  /* enable vh fix */
}

configuration

as a string

You can pass the CSS var name as a param to vhCheck() (default vh-offset)

vhCheck('browser-address-bar')

In your CSS you will have to reference:

main {
  min-height: 100vh;
  min-height: calc(100vh - var(--browser-address-bar, 0px));
}

as an object

vh-check allows you to have more control by passing a configuration object.

vhCheck({
  cssVarName: 'vh-offset',
  force: false,
  bind: true,
  redefineVh: false,
  updateOnTouch: false,
  onUpdate: function noop() {},
})

cssVarName

type: string
default: 'vh-offset'

Change the CSS var name

force

type: boolean
default: false

Set the CSS var even if 100vh computation is good

bind

type: boolean
default: find

Automatically bind to orientationchange event

redefineVh

type: boolean
default: false

Change the CSS var value. Instead of being the total size of the gap, it will be 1% of the real window size.
You can find more explanation in this CSS Trick article

⚠️ Important

If you don't set a cssVarName, the CSS custom property will be named vh instead of vh-offset.
So your CSS should be:

.my-element {
  height: 100vh;
  height: calc(var(--vh, 1vh) * 100);
}

updateOnTouch

type: boolean
default: false

Add an event listener on touchmove to recompute the sizes

⚠️ Important

• This can impact your website performances as changing sizes will make your browser reflow
• if options.bind is false, this will be ignored as well

onUpdate

type: function
default: function noop(){}

you can specify a callback which will be called with an updated vh-check object every time a computation occurre.

about browser support

This library require requestAnimationFrame which is IE10+ You'll need a polyfill if you want to support older browsers

• vh unit – supported since IE9+
• calc – supported since IE9+
• CSS custom properties – supported since IE Edge and iOS 9.3+ IE11 & below will need a fallback without CSS var
• concerned browsers – as for now:
  • Safari since iOS7+
  • Chrome Android >= v56

To sum it up:

Browser	Library will work	CSS Custom property
<= IE 9	❌	❌
IE 10 & IE 11	✅	❌
IE Edge	✅	✅
< iOS 9.3	✅	❌

demo

github pages

https://hiswe.github.io/vh-check/

local

you'll need node

• clone the project
• npm install
• npm start
• go to: http://localhost:8080

caveats

On iOS only, Chrome & Firefox will change dynamically the size of 1vh depending on the display of the address bar.
Thus the library will return a not needed value.

If you want to prevent your vh's components to resize, you could fix the size of the unit like this:

vhCheck({
  bind: false,
  redefineVh: true,
})

.my-div {
  height: calc(var(--vh, 1vh) * 100);
}

other stuff

changelog

See CHANGELOG.md

migrating

See MIGRATING.md

run the tests

• clone the project
• npm install
• npm test

thanks

• Chris Butterworth for the contribution

related

• ios-inner-height