class Bases {
    getData() {
       // get some data and return
       data = 'hello';
       return data;
    }
 
    process() {
        let greeting = this.getData();
        console.log(greeting);
    }

    start() {
        setInterval(this.process, 5000)
    }
}

let b = new Bases;
b.start();

I want to call function 'process' so that it prints 'hello' every 5 seconds, however when i call b.start(), i always get this error:

TypeError: this.getData() is not a function

When i call b.process() instead of b.start() it works, but calling it in an interval always gives me the error. Any help is appriciated