如何使用jQuery檢查ID是否存在?

本文翻译自 bbb25 查看原文 2009-08-09 34251 html/html/ javascript/javascript/ jqueryjquery

I want to have a line of code similar to below:

我想要一行代碼如下所示:

var name = $('#input-name').attr("value");

However, the id 'input-name' is not guaranteed to exist. How do I check for its existence so that the assignment does not throw an error?

然而，id 'input-name'並不保證存在。如何檢查它的存在性，使賦值不會拋出錯誤?

4 个解决方案

if ($('#input-name').length) {
  // do something
}

Check for .length or .size() on the object. The select won't fail, jQuery will always return an object.

檢查對象上的.length或.size()。選擇不會失敗，jQuery將始終返回一個對象。

In my test the assignment didn't cause an error, it simply returned undefined.

在我的測試中，賦值沒有導致錯誤，只是返回了未定義的值。

In which case the solution would be the following:

在這種情況下，解決辦法如下:

var name = $('#input-name').attr("value");
if (name) {
  // blah blah
}

Or maybe:

或者:

var name = $('#input-name').attr("value") || 'defaultValue';

... if that makes sense in your case.

…如果這對你的情況有意義的話。

var name;
if ($('#input-name').length > 0)   
name= $('#input-name').attr("value");

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