First Steps

First steps with nut.js - from installation to automating mouse movement

Prerequisites


nut.js comes with a pre-built version of OpenCV for your respective target platform.
In order to use these pre-compiled bindings, certain runtime conditions have to be met.

Windows


In order to install nut.js on Windows, please make sure to have the Microsoft Visual C++ Redistributable installed.

In case you're running Windows 10 N, please make sure to have the Media Feature Pack installed as well.

macOS


On macOS, Xcode command line tools are required.
You can install them by running:

1xcode-select --install

Attention:

In case you're experiencing problems like your mouse not moving or your keyboard not typing,
please make sure to give the process you're executing your tests with accessibility permissions.

nut.js will give you a subtle hint in case permissions are lacking:

##### WARNING! The application running this script is not a trusted process! Please visit https://github.com/nut-tree/nut.js#macos #####

When an application wants to use accessibility features, a permission pop-up should be shown.
If not, you could try to manually add the application you're running the script from.

Settings -> Security & Privacy -> Privacy tab -> Accessibility -> Add...

For example, if you want to execute your node script in e.g. iTerm2, you'd have to add iTerm.app to the list.
When running your script from a built-in terminal in e.g. VSCode or IntelliJ, you'd have to add the respective IDE.

accessibility permissions screenFigure: accessibility permissions screen

Linux


Depending on your distribution, Linux setups may differ.

In general, nut.js requires

  • libXtst

Installation on *buntu distributions:

1sudo apt-get install build-essential libxtst-dev

Setups on other distributions might differ.

node


nut.js is built and tested against various versions of node.
However, for best compatibility, it's recommended to run the latest available LTS version of node (lts/gallium at the time of writing) and using a version manager like nvm.

Installation


With our prerequisites met, let’s continue installing.
The following steps are meant to be carried out in a dedicated directory of your choice.
We will simply refer to this directory as working directory.

npm project


Let’s first initialize a new npm project in our working directory by executing:

npm init

Feel free to fill out the interactive dialogue, but it’s not a hard requirement to continue the initial setup.

(You could even accept all defaults by running npm init -y)

Install nut.js


Running

1npm i @nut-tree/nut-js

or

1yarn add @nut-tree/nut-js

in our newly created npm project will install nut.js and its required dependencies.

Snapshot releases


nut.js also provides snapshot releases which allow testing of upcoming features.

Running

1npm i @nut-tree/nut-js@next

or

1yarn add @nut-tree/nut-js@next

will install the most recent development release of nut.js.

Attention: While snapshot releases are great to work with upcoming features before a new stable release, it is still a snapshot release.
Please bear in mind that things might change and / or break on snapshot releases, so it is not recommended using them in production.

Get Things Moving


Now that we're all set up it's time to get things moving!

In our working directory, let's create a new file, index.js.

Open it in your favourite editor and add the following lines to get started:

1const { mouse } = require("@nut-tree/nut-js");
2
3(async () => {
4    
5})();

mouse gives you control over your, well, mouse, so let's play around with it a bit!

Attention: nut.js is fully async, so in most examples you will see something like the above snippet, which is an async IIFE used as a workaround to use async / await at the top-level.

Simple Movement


1const { mouse, left, right, up, down } = require("@nut-tree/nut-js");
2
3(async () => {
4    await mouse.move(left(500));
5    await mouse.move(up(500));
6    await mouse.move(right(500));
7    await mouse.move(down(500))
8})();

nut.js provides a declarative API, so instead of explicitly stating where we want our cursor to be, we can use the MovementApi functions to move our cursor relative to our current position.

When executed via node index.js you'll see that your cursor moves along a square and ends up at its initial position.

Targeting Specific Points


Moving our cursor in up, down, left or right direction is a good start, but we're not sitting in front of an Etch A Sketch.
Let's see how we can target specific points on our screen.

1const { mouse, straightTo, Point } = require("@nut-tree/nut-js");
2
3(async () => {
4    const target = new Point(500, 350);
5    
6    await mouse.move(straightTo(target));
7})();

straightTo is another MovementApi function which takes a target Point and computes a straight line towards it, starting at our current cursor position.

Speeding up / Slowing down


In case you want to configure mouse movement speed to go faster / slower, every instance exposed by nut.js provides a config object.

The mouse config object allows you to configure movement speed measured in pixels per second.

1const { mouse, straightTo, Point } = require("@nut-tree/nut-js");
2
3(async () => {
4    mouse.config.mouseSpeed = 2000;
5    const fast = new Point(500, 350);
6    await mouse.move(straightTo(fast));
7    mouse.config.mouseSpeed = 100;
8    const slow = new Point(100, 150);
9    await mouse.move(straightTo(slow));
10})();

Beam me up, Scotty!


Sometimes we don't want to move along a path to reach a certain point.

In such cases, we can rely on setPosition to immediately change our cursor position to the provided Point.

1const { mouse, Point } = require("@nut-tree/nut-js");
2
3(async () => {
4    const target = new Point(500, 350);
5    await mouse.setPosition(target);
6})();

Summary


  • nut.js provides a mouse instance to control your cursor.
  • Movement speed in pixels / second is configurable via the config object.
  • It provides a high-level MovementApi for easy relative mouse movement.
  • For fast changes of cursor position, setPosition is the right tool.

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