setInterval and setTimeout in Typescript

问题:

I am learning Typescript and am trying to print a console message a number of times over a period of time. But in my test this happens once, you know the reason?

The code is below:

 class Class {
    private msg: string;
    constructor(msg: string) {
        this.msg = msg;
    }
    private printMsg(): void {
        console.log(this.msg);
    };
    public repeatMsg(): void {
        let intervalo = setInterval(this.printMsg(), 2000);
        setTimeout(function() {
            clearInterval(intervalo);
        }, 40000);
    }
}

let test: Class;
test = new Class("Hello");
test.repeatMsg();

回答1:

The problem in your code is there:

setInterval(this.printMsg(), 2000);

setInterval accepts a function as a first parameter. Expression this.printMsg() is a call of the function, and is void actually. There are two ways to fix it. Use lambda:

setInterval(() = > this.printMsg(), 2000);

Or use bind:

setInterval(this.printMsg.bind(this), 2000);