ajax的status为201依然触发jquery的error事件的问题

昨天在调试一个ajax的时候发现，即使status是201,仍然会触发jquery的error事件。statusText是"parseerror".

通过在stackoverflow上查询，戳这里。

加上参数

dataType："text"

就可以解决。

而问题产生的原因在评论里写的也很详细。但是并不对，他弄错了convert的位置，在jquery判断状态码前，就已经进行了ajaxConvert。

 // Determine if successful，判断status的大小
        isSuccess = status >= 200 && status < 300 || status === 304;

        // Get response data
        if (responses) {
            response = ajaxHandleResponses(s, jqXHR, responses);
        }

        // Convert no matter what (that way responseXXX fields are always set)，在此处对response的data进行转化。下面附有ajaxConvert的源码。
        response = ajaxConvert(s, response, jqXHR, isSuccess);

        // If successful, handle type chaining
        if (isSuccess) {

            // Set the If-Modified-Since and/or If-None-Match header, if in ifModified mode.
            if (s.ifModified) {
                modified = jqXHR.getResponseHeader("Last-Modified");
                if (modified) {
                    jQuery.lastModified[cacheURL] = modified;
                }
                modified = jqXHR.getResponseHeader("etag");
                if (modified) {
                    jQuery.etag[cacheURL] = modified;
                }
            }

            // if no content
            if (status === 204 || s.type === "HEAD") {
                statusText = "nocontent";

                // if not modified，判断状态是否为304

            } else if (status === 304) {
                statusText = "notmodified";

                // If we have data, let‘s convert it。
            } else {
                statusText = response.state;
                success = response.data;
                error = response.error;
                isSuccess = !error;
            }
        } else {
            // Extract error from statusText and normalize for non-aborts
            error = statusText;
            if (status || !statusText) {
                statusText = "error";
                if (status < 0) {
                    status = 0;
                }
            }
        }

function ajaxConvert( s, response, jqXHR, isSuccess ) {
	var conv2, current, conv, tmp, prev,
		converters = {},

		// Work with a copy of dataTypes in case we need to modify it for conversion
		dataTypes = s.dataTypes.slice();

	// Create converters map with lowercased keys
	if ( dataTypes[ 1 ] ) {
		for ( conv in s.converters ) {
			converters[ conv.toLowerCase() ] = s.converters[ conv ];
		}
	}

	current = dataTypes.shift();

	// Convert to each sequential dataType
	while ( current ) {

		if ( s.responseFields[ current ] ) {
			jqXHR[ s.responseFields[ current ] ] = response;
		}

		// Apply the dataFilter if provided
		if ( !prev && isSuccess && s.dataFilter ) {
			response = s.dataFilter( response, s.dataType );
		}

		prev = current;
		current = dataTypes.shift();

		if ( current ) {

			// There‘s only work to do if current dataType is non-auto
			if ( current === "*" ) {

				current = prev;

			// Convert response if prev dataType is non-auto and differs from current
			} else if ( prev !== "*" && prev !== current ) {

				// Seek a direct converter
				conv = converters[ prev + " " + current ] || converters[ "* " + current ];

				// If none found, seek a pair
				if ( !conv ) {
					for ( conv2 in converters ) {

						// If conv2 outputs current
						tmp = conv2.split( " " );
						if ( tmp[ 1 ] === current ) {

							// If prev can be converted to accepted input
							conv = converters[ prev + " " + tmp[ 0 ] ] ||
								converters[ "* " + tmp[ 0 ] ];
							if ( conv ) {

								// Condense equivalence converters
								if ( conv === true ) {
									conv = converters[ conv2 ];

								// Otherwise, insert the intermediate dataType
								} else if ( converters[ conv2 ] !== true ) {
									current = tmp[ 0 ];
									dataTypes.unshift( tmp[ 1 ] );
								}
								break;
							}
						}
					}
				}

				// Apply converter (if not an equivalence)
				if ( conv !== true ) {

					// Unless errors are allowed to bubble, catch and return them
					if ( conv && s.throws ) {
						response = conv( response );
					} else {
						try {
							response = conv( response );
						} catch ( e ) {
							return {
								state: "parsererror",
								error: conv ? e : "No conversion from " + prev + " to " + current
							};
						}
					}
				}
			}
		}
	}

	return { state: "success", data: response };
}

p.s.在ajax的同步请求情况下，onreadystatechang事件没有触发。

p.s.jquery判断了状态204（返回空）,或304（用户使用缓存文档）。

注释：

· 204 - No Content 没有新文档，浏览器应该继续显示原来的文档。如果用户定期地刷新页面，而Servlet可以确定用户文档足够新，这个状态代码是很有用的。

· 304 - Not Modified 客户端有缓冲的文档并发出了一个条件性的请求（一般是提供If-Modified-Since头表示客户只想比指定日期更新的文档）。服务器告诉客户，原来缓冲的文档还可以继续使用。