CodeMirror handleKillKey

foo.js

    _handleKillKey(codeMirror)
    {
        let handleTextChanges = (cm, changes) => {
            console.assert(this._expectTextChanges);
            this._expectTextChanges = false;
            console.log(changes);
            console.log("changes OFF, blur ON, move ON");
            let killedText;
            console.assert(changes.length === 1);
            let change = changes[0];
            console.assert(change.origin === "+delete");
            if (change.to.line === change.from.line + 1)
                killedText = "\n";
            else {
                console.assert(change.removed.length === 1);
                killedText = change.removed[0];
            }

            console.log("killed text: " + killedText);
            console.log("starts new sequence: " + !this._appendToKillSequence);
            cm.off("changes", handleTextChanges);
            cm.on("blur", handleBlur);
            cm.on("cursorActivity", handleCursorOrSelectionMovement);
            this._appendToKillSequence = true;
        };

        let handleBlur = (cm) => {
            this._appendToKillSequence = false;
            console.log("blurred");
            console.log("blur OFF, move OFF");
            cm.off("blur", handleBlur);
            cm.off("cursorActivity", handleCursorOrSelectionMovement);
        };

        let handleCursorOrSelectionMovement = (cm) => {
            if (this._expectTextChanges)
                return;

            this._appendToKillSequence = false;
            console.log("selection or cursor moved");
            console.log("blur OFF, move OFF");
            cm.off("blur", handleBlur);
            cm.off("cursorActivity", handleCursorOrSelectionMovement);
        };

        let keyHandled = (cm, name, event) => {
            console.log("keyHandled");
            cm.off("keyHandled", keyHandled);
        };

        console.log("Killing line");
        this._expectTextChanges = true;
        console.log("changes ON, blur OFF, move OFF");
        codeMirror.on("keyHandled", keyHandled);
        codeMirror.on("changes", handleTextChanges);
        codeMirror.operation()
        codeMirror.execCommand("killLine");
    }