遍历jQuery中的数组 [英] iterate over array in jquery

问题描述

我正在尝试对从列表中选择项目的用户进行一些验证.我想通过检查<li>是否已经在数组中来确保没有两次添加项.这是我正在尝试，但无法正常工作.

I'm trying to do some validation on a user selecting items from a list. I want to make sure an item is not added twice by checking if the <li> is already in the array. This is what I'm trying and its not working.

 $(".List").on("click", "li", function () {
 var i = 0;
 var checkArr = [];

 var div = $("#AddedItems");
 var parent = $(this).closest("ul");
 var itemtoadd = parent.find("[data-id]").attr("data-id");
 var name = parent.find("[data-name]").attr("data-name");

 alert(itemtoadd + name);//checking 

 var itemtoadd = ("<li id = " + itemtoadd + " class = \"itemAdd\">" + name + "</li>");

 checkArr.push(itemtoadd); //put one in to check against?
 checkArr.forEach(item)
 {
     if (item == itemtoadd)
         alert("this item has already been added");
     else {
         checkArr.push(itemtoadd);
         alert(itemtoadd);
         $(itemtoadd).appendTo(div);
     }
 }
 // div.html(itemtoadd);


 });

推荐答案

您在这里至少遇到三个问题:

You have at least three problems here:

1. 您未正确使用Array.forEach-它具有接受项的功能.
2. 在进行检查之前，您要立即添加要查找的项目.您将始终遇到alert情况.
3. 您正在使用checkArr作为局部变量-每次输入该函数都会得到一个空数组.

1. You aren't using Array.forEach correctly -- it takes a function that takes an item.
2. Immediately before you do your check, you're adding the item you're looking for. You will always hit the alert case.
3. You're using checkArr as a local variable -- you're getting an empty array each time you enter the function.

总而言之，您无需保留任何数组就可以实现您的目标.我相信您可以用以下方法替换从第一条警报开始的所有内容:

That all being said, you can accomplish your goal without keeping an array at all. I believe you can replace everything from your first alert down with this:

if ($('#' + itemtoadd, div).length == 0) {
    itemtoadd = ("<li id = " + itemtoadd + " class = \"itemAdd\">" + name + "</li>");
    div.append(itemtoadd);
}
else {
    alert("this item has already been added");
}

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