if (response && (response.status === 200 || response.status === 304 || response.status === 400)) { // 如果不需要除了data之外的数据，可以直接 return response.data return response }

这段代码是用来处理一个 HTTP 请求的响应结果的，首先判断响应的状态码是否为 200、304 或 400，如果是的话就返回响应对象本身（包含了除了数据之外的其他信息），否则返回 undefined。如果不需要获取除了数据之外的其他信息，可以直接返回响应对象中的 data 字段，即 response.data。

相关问题

xhr.onreadystatechange = function() { if (xhr.readyState === 4 && xhr.status === 200)什么意思

This code snippet sets a callback function for the `readystatechange` event of an `XMLHttpRequest` object (`xhr`). The `readystatechange` event is fired several times as the request progresses through different states, and the callback function is called each time to handle the response data.

The code checks if the `readyState` property of the `xhr` object is equal to 4, which means that the request has completed and the response data is available. If the condition is true, the callback function can access the response data using the `xhr.responseText` property and perform any necessary processing.

xhr.readyState === 4 && xhr.status === 200 在js里这个语句是什么意思

This statement is checking if the value of the `readyState` property of an `XMLHttpRequest` object is equal to 4.

In the context of AJAX (asynchronous JavaScript and XML) programming, the `readyState` property indicates the current state of the request. A value of 4 means that the request has been completed and the response is ready. This is also known as the "done" state.

Therefore, this statement is typically used in an event handler or a polling loop to detect when the request has finished and the response can be processed.