Project arrays of coordinates using Proj4JS

project-coordinate-arrays.js

// For use withhttp://proj4js.org/

	/** @typedef {(string|proj4.Proj)} Projection
	 * 
	 */

	/** @typedef {object} ThisProjectionInfo
	 * @property {?Projection} inPrj
	 * @property {?Projection} outPrj
	 */

	/** @typedef {(Number[]|Array<Array<Number>>|<Array<Array<Array<Number>>>)} ProjectableArray
	 * 
	 */

	/** For use with the Array.prototype.map() function.
	 * @param {ProjectableArray} a
	 * @this {ThisProjectionInfo}
	 */
	function projectMap(a) {
		/*jshint validthis:true*/
		return projectCoords(a, this.inPrj, this.outPrj);
		/*jshint validthis:false*/
	}


	/** projects coordinates in an array.
	 * @param {ProjectableArray} array - An array of numbers or an array containing arrays of numbers.
	 * @param {Projection} inPrj - input projection.
	 * @param {Projection} [outPrj] - output projection.
	 * @returns {ProjectableArray} - The projected version of the input array.
	 */
	function projectCoords(array, inPrj, outPrj) {
		var output;

		if (array && array.length) {
			if (array[0] instanceof Array) {
				output = array.map(projectMap, {
					inPrj: inPrj,
					outPrj: outPrj
				});
			} else if (typeof array[0] === "number") {
				output = proj4(inPrj, outPrj, array);
			}
		} else {
			output = array;
		}
		return output;
	}