getting TypeError: Cannot read property 'style' of undefined react

Asked Apr 13 '19 at 12:01

Active Apr 13 '19 at 12:06

Viewed 223 times

i am getting below error when use style in my react code

 TypeError: Cannot read property 'style' of undefined

i try to call the showSlides function . Error throws in style.

slides[this.slideIndex-1].style.display = "block";

code is :

showSlides(n) {
  var i;
  var slides = document.getElementsByClassName("mySlides");
  var dots = document.getElementsByClassName("dot");

  if (n > slides.length) {this.slideIndex = 1} 
  if (n < 1) {this.slideIndex = slides.length}
  for (i = 0; i < slides.length; i++) {
    slides[i].style.display = "none";  
  }
  this.slideIndex++;
  if (this.slideIndex > slides.length) {this.slideIndex = 1}    
  for (i = 0; i < dots.length; i++) {
    dots[i].className = dots[i].className.replace(" active", "");
  }
  slides[this.slideIndex-1].style.display = "block";  
  dots[this.slideIndex-1].className += " active";
  setTimeout(this.showSlides, 2000); // Change image every 2 seconds  
}

any syntax change in react js

edited Apr 13 '19 at 12:05

Anthony Kong

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asked Apr 13 '19 at 12:01

John Ken

@MaheerAli: added – John Ken Apr 13 '19 at 12:04
`slides` must be an empty array... so gives an error – UXDart Apr 13 '19 at 12:05
What's unclear in the error message? The object you are trying to reference `slides[this.slideIndex-1]` does not exist, you cannot invoke a method upon non-existing variable. This has nothing to do with react. – Mike Doe Apr 13 '19 at 12:05
Possible duplicate of [Detecting an undefined object property](https://stackoverflow.com/questions/27509/detecting-an-undefined-object-property) – Mike Doe Apr 13 '19 at 12:07
is slides[this.slideIndex-1] check this first – patelarpan Apr 13 '19 at 12:59

getting TypeError: Cannot read property 'style' of undefined react

0 Answers0