gistfile1.js

// this example script uses a user-submitted script to modify image
// data from a canvas in which the user drew art

var sandbox   = new JSandbox(),
userArt       = document.getElementById("userArt").getContext("2d"),
imageData     = userArt.getImageData(0, 0, userArt.width, userArt.height);

sandbox.load("user-submitted-script.js", function () { // onload
	this.eval("doStuffWithImageData(input)", function (modifiedImageData) {
		userArt.putImageData(modifiedImageData, 0, 0);
		this.terminate();
		sandbox = null;
	}, imageData);
});