irishmarineinstitute / erddap-leaflet-velocity-demo Goto Github PK

Reported by @fullergalway

Allows reading from non-CORS enabled Erddap servers

Reported by @fullergalway

Reported by @fullergalway

While this now uses a JSONP formatted response, it doesn't get around CORS when accessing other ERDDAP servers as it still is using the fetch API.

JSONP gets around CORS by loading data within a script tag and when the script finishes loading it fires the JSONP callback function (erddapData) that it has been wrapped in.

Starting with this, this function will work to load JSONP data from ERDDAP and return a Promise, that you can .then( off of and not be limited by CORS.

function jsonp(url) {
    return new Promise(function(resolve, reject) {
        let script = document.createElement('script')
        const name = "_jsonp_" + Math.round(100000 * Math.random());
        //url formatting
        if (url.match(/\?/)) url += "&.jsonp="+name
        else url += "&.jsonp="+name
        script.src = url;

        window[name] = function(data) {
            resolve(data);
            document.body.removeChild(script);
            delete window[name];
        }
        document.body.appendChild(script);
    });
}

I believe a remaining limitation will be when accessing http from https sites as that will be blocked by mixed content.

Re #1