xmlHttpRequest.open("GET",url,true); Uncaught TypeError: Cannot read properties of undefined (reading 'open')

This error occurs when the xmlHttpRequest variable is not defined or is null. This can happen if the variable is not declared or if it is not properly initialized before calling the open() method.

To fix this error, make sure that the xmlHttpRequest variable is properly declared and initialized before using it to call the open() method. For example:

var xmlHttpRequest = new XMLHttpRequest();
xmlHttpRequest.open("GET", url, true);

This code creates a new XMLHttpRequest object and then calls the open() method with the specified parameters. Make sure to replace "url" with the actual URL you want to retrieve data from.

相关问题

Uncaught TypeError: Cannot read properties of undefined (reading 'open')

This error occurs when you try to access a property or method of an undefined variable or object. In this case, it seems like you are trying to access the 'open' property of an undefined variable or object.

To fix this error, you need to check if the variable or object is defined before trying to access its properties or methods. You can use an if statement to check if the variable or object exists before trying to access its properties or methods.

For example:

let xhr = new XMLHttpRequest();

if (xhr) {
  xhr.open('GET', 'https://example.com/api');
  // rest of the code
}

In this example, we check if the xhr variable exists before calling the 'open' method. If xhr is undefined, the code inside the if statement will not be executed, preventing the 'Cannot read properties of undefined' error.

xhr.js:87 Uncaught (in promise) TypeError: Cannot read properties of undefined (reading 'toUpperCase')

xhr.js是一个用于发送XMLHttpRequest请求的JavaScript库。在你提供的错误信息中，"xhr.js:87"指的是错误发生在xhr.js文件的第87行。

错误信息"Uncaught (in promise) TypeError: Cannot read properties of undefined (reading 'toUpperCase')"表示在该行代码中，尝试读取一个未定义的属性（'toUpperCase'），导致了类型错误（TypeError）。

这种错误通常发生在尝试对一个undefined或null值进行属性访问时。可能的原因包括：

1. 未正确初始化变量或对象。
2. 异步操作返回了一个未定义的值。
3. 对象属性名拼写错误或不存在。

为了更准确地定位问题，需要查看xhr.js文件的第87行代码以及相关代码上下文。可以尝试使用浏览器的开发者工具来调试并查看具体的错误位置和原因。