Is it possible to detect the document changed or not

1

I am using this code to save yDoc change to database:

 ydoc.on('update', (update, origin) => {
        try {
            let snapshot: Y.Snapshot = Y.snapshot(ydoc);
            let snap: Uint8Array = Y.encodeSnapshot(snapshot);
            // https://discuss.yjs.dev/t/save-the-yjs-snapshot-to-database/2317
            let snapBase64 = btoa(String.fromCharCode(...new Uint8Array(snap)));
            let params: TexFileVersion = {
                file_id: editorAttr.docId,
                name: editorAttr.name,
                project_id: editorAttr.projectId,
                content: ytext.toString(),
                action: 1,
                snapshot: snapBase64
            };
            throttledFn(params);
        } catch (e) {
            console.log(e);
        }
    });

this function works fine, I can save the document snapshot to database. but now the update will trigger when open the yDoc no matter edit the document or not. What should I do to detect the document change, only trigger the save to database action when the document changed.

2

You could try loading the stored snapshot and using equalSnapshots to compare it directly with the in-memory snapshot.

1 Like
3

I have tried like this, seems the snapshot will never been equal:

ydoc.on('update', (update, origin) => {
        try {
            let snapshot: Y.Snapshot = Y.snapshot(ydoc);
            let snap: Uint8Array = Y.encodeSnapshot(snapshot);
            // https://discuss.yjs.dev/t/save-the-yjs-snapshot-to-database/2317
            let content = String.fromCharCode(...new Uint8Array(snap));
            let snapBase64 = btoa(content);
            let lastsnapshot = localStorage.getItem("lastsnapshot");
            if(snapBase64 === lastsnapshot){
                // never run into this
                debugger
                return;
            }
            if(lastsnapshot){
                let cached = base64ToUint8Array(lastsnapshot);
                const decoded = Y.decodeSnapshot(cached);
                let equal = Y.equalSnapshots(decoded,snapshot);
                if(equal){
                    // never run into this
                    debugger
                    return;
                }
            }
            let editorText = ytext.toString();
            let lasteditortext = localStorage.getItem("lasteditortext");
            if(lasteditortext === editorText){
                // will run into this
                debugger
                return;
            }
            let params: TexFileVersion = {
                file_id: editorAttr.docId,
                name: editorAttr.name,
                project_id: editorAttr.projectId,
                content: editorText,
                action: 1,
                snapshot: snapBase64
            };
            // https://discuss.yjs.dev/t/is-it-possible-to-detect-the-document-changed-or-not/2453
            localStorage.setItem("lastsnapshot",snapBase64);
            localStorage.setItem("lasteditortext",editorText);
            throttledFn(params);
        } catch (e) {
            console.log(e);
        }
    });