js: add bare bones js stuff

1 files changed, 32 insertions, 0 deletions

diff --git a/fretboard.mjs b/fretboard.mjs
new file mode 100644
index 0000000..c58543c
--- /dev/null
+++ b/fretboard.mjs
@@ -0,0 +1,32 @@
+function fretChanged(e) {
+    console.log('fret changed', e);
+}
+
+let mousedownVal = undefined;
+
+function mousedown(e) {
+    // at mousedown time, the form hasn't yet been changed. to support
+    // deselecting elements, we need to know what the previous
+    // selection was, so store it here.
+    //
+    // it'd be nice to be able to do this just in the click handler.
+    mousedownVal = e.target.checked;
+}
+
+function click(e) {
+    const elt = e.target;
+    // if this element was selected at mousedown time, deselect it
+    // now.
+    if (mousedownVal) {
+        elt.checked = false;
+    }
+}
+
+export default function Fretboard(form) {
+    console.debug('Fretboard()', form);
+    form.onchange = fretChanged;
+    form.querySelectorAll('input[type="radio"]').forEach(elt => {
+        elt.onmousedown = mousedown;
+        elt.onclick = click;
+    });
+}