PaperScript Interoperability

Both PaperScript and JavaScript have access to the Window scope, therefore you can use window.globals<code> from the JavaScript and <code>globals<code> from PaperScript to pass information back and forth.

<title>JavaScript <=> PaperScript example</title>

<code mode="text/html">
<!DOCTYPE html>
<script type="text/javascript" src="js/paper.js"></script>
<script type="text/paperscript" canvas="myCanvas">
// Create a Paper.js Path to draw a line into it:
var path = new Path();
path.strokeColor = 'black';
var start = new Point(100, 100);

// Use the global variables a and b defined in the JavaScript
path.lineTo(start + [ globals.a, globals.b ]);

// Define a global function inside the window scope.
globals.lineTo = function(c,d) {
path.lineTo(new Point(c, d));

<script type="text/javascript">
// To avoid race problem, the following should not be in window.onload as the PaperScript might run before.
window.globals = { a:50, b:-50 };

// Update the path from the JavaScript code.
window.onload = function() {
document.getElementById('lineToBtn').onclick = function() {
let x = Number(document.getElementById('x').value);
let y = Number(document.getElementById('y').value);
<input type="range" id="x" from="0" to="150" default="75"></input>
<input type="range" id="y" from="0" to="150" default="75" ></input>
<button type="number" id="lineToBtn">LineTo</button>
<canvas id="myCanvas" resize></canvas>


The scopes of multiple PaperScript is different and can collides. If you create two functions with the same name in two PaperScripts, the second will overwrite the first one.

Thus you might want to create another variable in the window for each PaperScript running to avoid the confusion.