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Is there an "exists" function for jQuery?（47个答案）
20小时前关门了。
如何编写一个函数来检查某个id的元素是否存在。我在一个数组中设置了这些id来进行验证：令车数组=["车-0"，"车-1"，"车-2"，"车-3"];
JavaScript语言：

//=== === === Cart === === ===\\
      $(document).ready(function() {
        //========= checking the presence of items in the cart when the page is loaded =========\\
        if(document.getElementById('myDIV').childElementCount == 0) {
          document.getElementById('myDIV').innerHTML = "cart is empty";
        }
        
        const element = document.getElementById('myDIV');
        const numberOfChildren = element.childElementCount; //====== Number of items in the cart

        //========= Changing ::before for the cart when the page is loaded =========\\
        for(var i = 0; i < numberOfChildren; i++) {
          CartCount++;
        }
        document.getElementById("CountCartS").setAttribute('CartCountS', CartCount);

        //========= Add to cart (number changes) =========\\
        $("#button-count").click(function () {
          CartCount++;
          document.getElementById("CountCartS").setAttribute('CartCountS', CartCount);
        });

        const button = document.querySelector('#button');
        
        button.addEventListener('click', function() {
          for(var i = 0; i < numberOfChildren; i++) {
            const parent = document.getElementById('myDIV');
            const child = parent.children[i];
            
            if(parent.childElementCount > 0) {
              if(child.id == CartArray[i]) {
                alert(child.id + " --- there is a div with this id");
              }
              else if(child.id != CartArray[i]) {
                alert(child.id + " --- does not have a div with that id");
              }
            }
            else if(parent.childElementCount == 0) {
              document.getElementById('myDIV').innerHTML = "cart is empty";
            }
            else {
              alert("Error");
            }
          }
        });
      });

代码不适合stackoverflow，所以我添加了一个到codepen的链接：https://codepen.io/SHvari_David_Simba/pen/JjBNXzp
我尝试通过数组中的id检查该项是否存在，但没有任何结果