setInterval and setTimeout in Typescript

Question

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();

Remove the (), you're calling the function immediately, setInterval expects a function reference, like you provided via anonymous function in the timeout — Sterling Archer
– Sterling Archer, Commented Mar 4, 2018 at 3:05
Removing () would break this.msg. Using this.pringMsg.bind(this) would work though. — Jake Holzinger
– Jake Holzinger, Commented Mar 4, 2018 at 3:14

Jake Worth · Accepted Answer · 2018-12-19 21:16:57Z

15

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);

edited Dec 19, 2018 at 21:16

Jake Worth

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answered Mar 4, 2018 at 5:02

Pavel

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