问使用javascript使div出现或消失

EN

var serviceType = document.querySelectorAll(".serviceType");
var serviceTypeArray = Array.prototype.slice.call(serviceType); // this will 
 //change your serviceType from a nodelist to an Array.
var serviceDescription = document.querySelectorAll(".list"); // to grab the 
 //list of descriptions and make it into an "array"

for ( i = 0 ; i < serviceTypeArray.length ; i++) {
 var services = serviceTypeArray[i]; // I created this variable to store the 
   // variable "i"
 services.addEventListener( "click" , displayServices); }
  // created this "for loop" to loop through every element inside the array 
 //and give it the "click" function

function displayServices() {
  var servicePosition = serviceTypeArray.indexOf(this); // when we click the 
    // event, "this" will grab the position of the clicked item in the array
  if (serviceTypeArray[servicePosition].hasAttribute("id") == false) { // 
   //  the hasAttribute returns values of true/false, since initially the 
   // serviceTypeArray didn't have the "id" , it returns as false
  serviceTypeArray[servicePosition].setAttribute( "id" , "hide"); // I've 
   // added the "setAttribute" function as a unique indicator to allow 
   // javascript to easily hide and show based on what we are clicking
  serviceDescription[servicePosition].style.display = "block"; // When you 
   //click one of the serviceType, it returns an the index number (aka the 
   // position it is inside the arrayList)
   //this gets stored inside servicePosition(aka the actual number gets 
  //  stored).
  // Since i've made an array to store the the description of each service, 
  // their position in the array correspond with the service's position 
  //inside the serviceType array made earlier; therefore, when I press one 
  // particular serviceType (ie i clicked on "business formation"), the 
  // appropriate text will pop up because the position of both the name and 
  // its description are in the same position in both arrays made
 } else if (serviceTypeArray[servicePosition].hasAttribute("id") == true ) { 
  //since the serviceType now has an attribute, when we check it, it'll come 
  // back as true
    serviceTypeArray[servicePosition].removeAttribute("id"); //we want to 
    // remove the id so next time we click the name again, the first "if" 
    // condition is checked
     serviceDescription[servicePosition].style.display = "none"; //this is    
     //  so that the display goes back to "none"
      }
    }