js is not defined

当你在JavaScript代码中遇到"Uncaught ReferenceError: is not defined"这个错误时，它通常意味着你在尝试访问或调用一个未声明或者在当前作用域内不存在的变量或函数。"is"在这个上下文中并没有被定义，所以JavaScript引擎无法找到你试图使用的"defined"属性或函数。

例如，如果你有以下代码：

if (isDefined()) {
    // ...
}

但没有先定义`isDefined()`，就会报错，因为`is`没有被声明为一个函数或变量。正确的做法应该是先确保变量或函数已经被声明：

function isDefined(value) {
    return typeof value !== 'undefined';
}

if (isDefined(someVariable)) {
    // ...
}

相关问题

clipboard js is not defined

It seems that you are encountering an error message saying "clipboard js is not defined." This error typically occurs when the Clipboard.js library is not properly loaded or referenced in your code.

To resolve this issue, make sure you have correctly included the Clipboard.js library in your HTML file before using any of its functionality. You can include it by adding the following script tag in the head or body section of your HTML file:

<script src="https://cdnjs.cloudflare.com/ajax/libs/clipboard.js/2.0.8/clipboard.min.js"></script>

Ensure that the source URL points to the correct version of Clipboard.js. After including the library, you should be able to use the Clipboard.js functions without encountering the "clipboard js is not defined" error.

Proj4js is not defined

这个错误通常是由于缺少 Proj4js 库而导致的。你需要确保在使用 Proj4js 的代码中正确引入该库，并且该库的文件路径正确无误。你可以在头部添加以下代码来引入该库：

<script src="https://cdnjs.cloudflare.com/ajax/libs/proj4js/2.7.2/proj4.js"></script>