README.md

Rallax.js

Dead-simple parallax scrolling.

See a demo.

Usage

Follow these steps to get started:

1. Overview
2. Install
3. Call
4. Review Options
5. Review API
6. Handling Page Refresh

Overview

Want to create dynamic parallax scrolling effects on your web page, without relying on jQuery?

Rallax.js makes it easy to create a parallax effect on a target HTML element, with great performance and no dependencies.

Install

Using NPM, install Rallax, and save it to your package.json dependencies.

$ npm install rallax.js --save

Then, import Rallax, naming it according to your preference.

import rallax from 'rallax.js'

Call

To generate the desired effect, call Rallax, passing in your element/target-selector and your desired options.

const options = { speed: 0.4 }
const parallax = rallax('.parallax', options)

// or:

const target = document.querySelector('.parallax')
const parallax = rallax(target, { speed: 0.4 })

Note: Rallax.js does not make any assumptions regarding the styling of the target element.

Options

You are not required to pass any options. All options come with sensible defaults, shown below:

{
  speed: 0.3,
  mobilePx: false
}

Explanation of each option follows:

• speed
• mobilePx

speed

Accepts a float number.

At a speed of 0, the target will scroll like a static element. At a speed of 1, the target will appear fixed (will move at the speed of scroll). At even higher speeds, the target will move quicker than the speed of scroll.

mobilePx

Accepts an integer, as number of pixels.

Pass this option if you want parallax for this target to automatically be disabled at a certain screen width.

API

Calling Rallax will return an object with a set of methods defined. Those methods are:

• stop
• start
• getSpeed
• changeSpeed
• when

stop

Calling stop() will pause the parallax effect on the target until the next time you call start().

const parallax = rallax('.parallax')

if (condition) {
  parallax.stop()
}

start

Calling start() will re-enable the parallax effect if you had previously disabled it. Note: calling start() will not re-enable the effect if you have disabled it with the mobilePx option.

const parallax = rallax('.parallax')
parallax.stop()

// some time later

parallax.start()

getSpeed

Returns the current speed of the target.

changeSpeed (speed)

Accepts a float.

Calling changeSpeed will change the speed of the target parallax effect.

// initialize the target at a speed of 0.6
const parallax = rallax('.parallax', { speed: 0.6 })

// change speed to 1, making the target appear fixed
parallax.changeSpeed(1)

when (condition, action)

Accepts a condition function and an action function.

Calling when will queue a condition and action onto the target, which will be evaluated before the target is scrolled. The when method is useful for setting up all kinds of special effects.

when methods can be chained together.

const parallax = rallax('.parallax')

// after reaching a certain position in the document, 
// increase the target's speed
parallax.when(
  () => window.scrollY > 400,
  () => parallax.changeSpeed(1)
)

// stop the parallax after a certain period of time
const startTime = new Date().getTime()

parallax.when(
  () => {
    const newTime = new Date().getTime()
    return newTime - startTime > 4000
  },
  () => parallax.stop()
)

Handling Page Refresh

Rallax.js will adapt to the refreshing of the page, and place targets where they would be normally if they were to scroll to the point of refresh.

However, if using changeSpeed in conjunction with when methods/conditionals, it's important to scroll to the top of the page when the user refreshes. Code to handle such a situation:

window.onbeforeunload = () => {
  window.scrollTo(0, 0)
  // alternatively, you can put an animation function here
  // that will bring user to the top of page
}

Browser Support

Rallax depends on the following browser APIs:

• requestAnimationFrame

Consequently, it supports the following natively:

• Chrome 24+
• Firefox 23+
• Safari 6.1+
• Opera 15+
• IE 10+
• iOS Safari 7.1+

License

MIT. © 2018 Christopher Cavalea