utils.js

var utils = {
	groupBy : function(xs, key) {
		return xs.reduce(function(rv, x) {
		(rv[x[key]] = rv[x[key]] || []).push(x);
		return rv;
		}, {});
	},
	
	// Copies a string to the clipboard. Must be called from within an
	// event handler such as click. May return false if it failed, but
	// this is not always possible. Browser support for Chrome 43+,
	// Firefox 42+, Safari 10+, Edge and Internet Explorer 10+.
	// Internet Explorer: The clipboard feature may be disabled by
	// an administrator. By default a prompt is shown the first
	// time the clipboard is used (per session).
	// https://stackoverflow.com/a/33928558/6419007
	copyToClipboard : function(text, log) {
		if (window.clipboardData && window.clipboardData.setData) {
			// Internet Explorer-specific code path to prevent textarea being shown while dialog is visible.
			return window.clipboardData.setData("Text", text);
		}
		else if (document.queryCommandSupported && document.queryCommandSupported("copy")) {
			var textarea = document.createElement("textarea");
			textarea.textContent = text;
			textarea.style.position = "fixed";  // Prevent scrolling to bottom of page in Microsoft Edge.
			document.body.appendChild(textarea);
			textarea.select();
			try {
				document.execCommand("copy");  // Security exception may be thrown by some browsers.
				log.append("<h2 class='ok'>Coordinates copied to clipboard!</h2><br/>\n");
				return;
			}
			catch (ex) {
				console.warn("Copy to clipboard failed.", ex);
				return prompt("Copy to clipboard: Ctrl+C, Enter", text);
			}
			finally {
				document.body.removeChild(textarea);
			}
		}
	},
	
	read_kml: function(url){
		return new ol.source.KML({
			projection : ol.proj.get('EPSG:3857'),
			url : url,
			extractAttributes : false,
			extractStyles : false
		});
	},
	
	polygon_style: function(color, alpha) {
		return new ol.style.Style({
			fill : new ol.style.Fill({
				color : 'rgba(255, 255, 255,' + alpha + ')'
			}),
			stroke : new ol.style.Stroke({
				color : color,
				width : 2,
				lineDash : [ 5, 10 ]
			}),
		});
	}
};