Arrow toggle

custom.js

// Toggle panel-title arrow script
arrowToggle();

function arrowToggle() {
  var panelTitle = document.getElementsByClassName("panel-title");
  var arrowDown = "arrow_drop_down";
  var arrowUp = "arrow_drop_up";

  for(var i = 0; i < panelTitle.length; i++) {
          panelTitle[i].addEventListener("click", function() {
        if(this.getElementsByClassName("arrow")[0].innerHTML === arrowDown) {
  	this.getElementsByClassName("arrow")[0].innerHTML = arrowUp;
  } else if (this.getElementsByClassName("arrow")[0].innerHTML === arrowUp) {
  	this.getElementsByClassName("arrow")[0].innerHTML = arrowDown;
  }
      });
  }
}