Cannot assign to read only property 'disconnectedHandler' of object '[object Object]

Question

I am trying to work with a timer in Salesforce Lightning. When I add it to the page, it throws the error of "render threw an error in 'c:serviceConsoleCaseTimer' [Cannot assign to read only property 'disconnectedHandler' of object '[object Object]']" I have no clue how to fix this error. Here is the code where I am getting this error:

set tabclosed(value){
        this._tabclosed = value;
        this.tabisclosed = this._tabclosed;
        if(this.tabisclosed){
            this.disconnectedHandler();
        }
    }


    constructor(params){
        super(params)

        this.disconnectedHandler = this.disconnectedHandler.bind(this)
        this.pauseTimer = this.pauseTimer.bind(this)
     }

    connectedCallback() {
        if(this.autoStart){              
            this.start();
        }
        window.addEventListener("beforeunload", this.disconnectedHandler); 
    }       

    // Function for detecting window navigation/closing 
    disconnectedHandler(){
        if(this.stime !== '00:00:00'){       
        this.stop();        
        newSession({caseId: this.recordId, timeVal: this.stime}).then(() => {
            })
            .catch(error => {
            });
        }
    }

I understand that the property is read only. I have tried to set the property writable : true as well.

Here are the links that I have tried: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Errors/Read-only https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/freeze https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/defineProperty

https://stackoverflow.com/questions/57591012/ngrx-cannot-assign-to-read-only-property-property-of-object-object Workspace Api not returning focused tab details

Thank you for any help!

Answer 1

set tabclosed(value){
        this._tabclosed = value;
        this.tabisclosed = this._tabclosed;
        if(this.tabisclosed){
            this.disconnectedHandler();
        }
    }


    constructor(params){
        super(params)

        this.disconnectedHandler()
        this.pauseTimer()
    }

    connectedCallback() {
        if(this.autoStart){              
            this.start();
        }
        window.addEventListener("beforeunload", this.disconnectedHandler); 
    }       

    // Function for detecting window navigation/closing 
    disconnectedHandler(){
        if(this.stime !== '00:00:00'){       
        this.stop();        
        newSession({caseId: this.recordId, timeVal: this.stime}).then(() => {
            })
            .catch(error => {
            });
        }
    }