XD text randomizer

xd_text_randomizer.js

function randomizeText(selection, documentRoot) {
    documentRoot.children.forEach(node => {
        // [1]
        if (node instanceof Artboard) {
            // [2]
            let artboard = node;

            let rectangles = artboard.children.filter(artboardChild => {
                // [3]
                return artboardChild instanceof Text;
            });
            rectangles.forEach(rectangle => {
                // [4]
                // const strLength = rectangle.text.length;
                // const random = Math.random().toString(36).replace(/[^a-z]+/g, '').substr(0, strLength);
                // console.log(random);
                const newText = rectangle.text
                    .split("")
                    .map(letter => {
                        if (!isLetter(letter)) {
                            return letter;
                        }
                        let newLetter = Math.random()
                            .toString(36)
                            .replace(/[^a-z]+/g, "")
                            .substr(0, 1);
                        if (letter === letter.toUpperCase()) {
                            newLetter = newLetter.toUpperCase();
                        }
                        return newLetter;
                    })
                    .join("");
                console.log(newText);
                rectangle.text = newText;
                // rectangle.text = random;
            });
        }
    });
}