@clvarley/simple-scroll

The small utility that aims to make scrolling to elements simple.

About

Getting the browser to scroll to a given element can be a pain. While APIs like Element.scrollIntoView and window.scroll can get us there, they can be fiddly to use and don't offer us much in the way of customisation.

Simple scroll is a small utility that offers a no-frills, no-nonesense way of easily scrolling elements into view.

Installation

Firstly, make sure to download the library like so:

npm install --save @clvarley/simple-scroll

After npm has installed the library, it can be imported into your projects as normal:

ES6 module*preferred

import {simpleScroll} from '@clvarley/simple-scroll';

CommonJS

const {simpleScroll} = require('@clvarley/simple-scroll');

Getting Started

Now that you have the library installed and imported, we can begin to use it. Simple scroll offers a very simple API, in it's most basic form it can be used as follows:

import {simpleScroll} from '@clvarley/simple-scroll';

const someElement = document.querySelector('#some-element-id');

simpleScroll(someElement);

Just pass the element you want to view and simpleScroll will scroll the window there!

When this code gets run - for example inside an event listener - the window will be softly scrolled to the #some-element-id. If that's all you need, you can stop reading here and get building!

Options

However, it's likely you will want to modify the default behavior of simpleScroll to better suit your needs. The behaviour of simpleScroll can be customised by passing an options object through via the (optional) second parameter.

import {simpleScroll} from '@clvarley/simple-scroll';

const someElement = document.querySelector('#some-element-id');

simpleScroll(someElement, {
    duration: 2500,
    padding: 32
});

Here we've modified the default scroll behaviour. Now, the scroll will happen over the course of 2500 milliseconds (2.5s) and will leave 32px of padding above the element. (To accommodate for a fixed navbar, for example)

At the current time there are only 3 properties that can be set, but we hope to expose more in the future.

| Property | Type | Purpose | Default | | :------- | :--- | :------ | :------ | | duration | number | Time (in milliseconds) the scroll animation should take* | 0 | | padding | number | Padding (in pixels) to be left above the element | 0 | | focus | boolean | Whether or not to focus the element after scroll | false | | timing | function | Function used to control how the animation will be timed | TIMING_EASE_IN_OUT |

Caveats

As standard simpleScroll respects the prefers-reduced-motion setting. On systems where this flag has been enabled the duration and timing options are silently ignored, with control instead being handled by the default browser scrolling behaviour.

If you find your scroll animations aren't respecting the duration option this may be why.

Timing

By default, simpleScroll uses a cubic ease-in-out curve for its animation (similar to how properties animate when using the ease-in-out value for CSS transitions). This is a good general "all rounder" and looks adequate in most places, but we also provide a set of other animation styles should you wish to use them.

Linear

Linear timing, with no acceleration or change in speed over the course of the animation. Scrolls straight to the target and stops.

simpleScroll(someElement, {
    timing: simpleScroll.TIMING_LINEAR
});

Ease-in

Timing with a slow start that accelerates. Gets faster over time and comes to a sharp stop at the target element.

simpleScroll(someElement, {
    timing: simpleScroll.TIMING_EASE_IN
});

Ease-out

Timing with a fast start that decelerates. Gets slower over time and comes to a gentle stop at the target element.

simpleScroll(someElement, {
    timing: simpleScroll.TIMING_EASE_OUT
});

Ease-in-out

The default.

Timing that accelerates at first, then decelerates as it approaches the end. Starts slow, picking up pace until the halfway mark then slowing down and gently stopping at the target element.

simpleScroll(someElement, {
    timing: simpleScroll.TIMING_EASE_IN_OUT
});

Custom Timing

Not happy with the defaults provided? You can also specify your own timing!

Passing a function of your own as the timing option is also allowed. Your custom callback must take one argument, a decimal number representing the current time elapsed between 0 and 1 (0 for just started, 0.5 for halfway, 1 for finished and so on) and must return a number within the same bounds (0 to 1) that represents how far you wish the animation to have progressed.

For those of you familiar with TypeScript the signature should look like this:

function myTimingCallback(elapsed: number): number {
    /* your logic here */
};

For inspiration, and for ideas of the sort of thing you might want to try, why not take a look at some of the examples on easings.net.