使用香草JS AJAX请求访问本地JSON文件时出现CORS错误? [英] CORS error when accessing local JSON file using vanilla JS AJAX request?

问题描述

我正在尝试使用香草JS AJAX请求从本地存储的JSON文件中拉回JSON字符串(特别是尝试不使用JQuery)-以下代码基于

I am trying to use a vanilla JS AJAX request to pull back a JSON string from a locally stored JSON file (specifically trying not to use JQuery) - the below code is based on this answer - but I keep getting an error in the Chrome console (see below). Any ideas where I'm going wrong? I have tried changing the positioning of the xhr.open & .send requests, but still get error messages. I suspect the issue lies with the .send() request?

//Vanilla JS AJAX request to get species from JSON file & populate Select box
function getJSON(path,callback) {

    var xhr = new XMLHttpRequest();                                         //Instantiate new request

    xhr.open('GET', path ,true);                                            //prepare asynch GET request
    xhr.send();                                                             //send request

    xhr.onreadystatechange = function(){                                    //everytime ready state changes (0-4), check it
        if (xhr.readyState === 4) {                                         //if request finished & response ready (4)
            if (xhr.status === 0 || xhr.status === 200) {                   //then if status OK (local file || server)
                var data = JSON.parse(xhr.responseText);                    //parse the returned JSON string
                if (callback) {callback(data);}                             //if specified, run callback on data returned
            }
        }
    };
}
//-----------------------------------------------------------------------------

//Test execute above function with callback
getJSON('js/species.json', function(data){
    console.log(data);
});

Chrome中的控制台抛出此错误:

The console in Chrome is throwing this error:

"XMLHttpRequest无法加载文件:///C:/Users/brett/Desktop/SightingsDB/js/species.json.仅协议方案支持跨源请求:http，数据，chrome，chrome扩展名，https ，chrome-extension-resource."

"XMLHttpRequest cannot load file:///C:/Users/brett/Desktop/SightingsDB/js/species.json. Cross origin requests are only supported for protocol schemes: http, data, chrome, chrome-extension, https, chrome-extension-resource."

感谢您提供任何见解-非常感谢.

Would be grateful for any insights - many thanks.

推荐答案

基本上，正如Felix，错误消息(MSG)等在下面说的那样-根本无法针对本地文件运行AJAX请求.

Basically as Felix, error msg, et al below say - simply can't run an AJAX request against a local file.

谢谢.

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