What's the meaning of the little JavaScript code?

JavaScript
1

What does the += ???

function plusSlides(n) {
showSlides(slideIndex += n);
}

2

Hi,

+= is a shorthand assignment operator.

In your example, slideIndex += n is the shorthand form for slideIndex = slideIndex + n

Refer to this link for more info: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Assignment_Operators