OPeNDAP protocol allows publishing huge datasets over internet. The protocols allows describing and querying data in various formats.
This library is designed to allow querying DAP dataset in AJAX based on the url. Main library code is from Roberto De Almeida's jsdap project on google code.
The script is packed as UMD module and transpile down to ES5 (dist/jsdap). However, you can only use it as ES6 module or AMD module. Since
the script relies on window.XMLHttpRequest, it is not available on NODE environment.
The dist/index.html is a good quickstart to load the libraries. Notice also that the cross domain limitations apply to OPeNDAP servers and thus requests must be properly managed or CORS enabled.
A quick start (make sure you have yarn or npm install), following is example with yarn:
// Download the dependencies (in the proj folder)
$ yarn
// Then you bring the webpack-dev server up and checkout the example
$ yarn serve
// If you want to rebuild the dist again, then
$ yarn build
To load a dataset the loadData function can be used this way (ES6 exampe) :
import JsDap from './dist/jsdap.js';
// if you want the IE_HACK, set the flag as true
let jsdap = new JsDap(false);
jsdap.loadData("http://www.example.com/dapserver/mydataset.nc.dods?time[1][1:5]",
function(data) {
console.log("Received data");
console.log(data);
});
Notice that the url MUST be a .dods request and that you CAN add additionnaly DAP query.
To only load the dataset (ie. information about the structure of data) :
import JsDap from './dist/jsdap.js';
// if you want the IE_HACK, set the flag as true
let jsdap = new JsDap(false);
jsdap.loadDataset("http://www.example.com/dapserver/mydataset.nc.dds",
function(info) {
console.log(info);
});
Notice that the url MUST be a .dds request and you CANNOT add additonnal DAP query/
An extra parameter can be added to send additionnal headers to the request.
Of cause, you can still go with the old school way, load the script into the <script> tag,
there you go:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>OpenDap</title>
<script type="text/javascript" src="jsdap.js"></script></head>
<body>
<script type="text/javacript">
// disable IE_HACK as default
var jsdap = new JsDap(false);
// if you want IE_HACK, just set the flag as true during initialize
// var jsdap = new JsDap(true);
// load data
jsdap.loadData("http://www.example.com/dapserver/mydataset.nc.dods?time[1][1:5]",
function(data) {
console.log("Received data");
console.log(data);
});
// load dataset
jsdap.loadDataset("http://www.example.com/dapserver/mydataset.nc.dds",
function(info) {
console.log(info);
});
</script>
</body>
</html>
- Your requests fail ? Careful about cross domain requests
- You have parsing errors in loadData ? Ensure you passed in .dods request not .ascii or other.
- You have parsing errors with loadDataset ? Ensure you are doing a .dds request.
Not enought ? Contact me at [email protected] or http://obenhamid.me