viewBox is an AngularJS directive which adds support for using an expression for the SVG viewBox, by using `data-view-box` which sets `viewBox` attribute. Code borrowed from http://stackoverflow.com/a/14596319

angular-view-box-directive.js

angular
	.module('directives.viewBox', [])
	.directive('viewBox', [
		/**
		 * @ngdoc directive
		 * @name directives.viewBox.directive:viewBox
		 * @description
		 * Supports using expression for SVG viewBox, by
		 * using `data-view-box` which sets `viewBox` attribute.
		 * Code borrowed from http://stackoverflow.com/a/14596319
		 * @element SVG
		 * @example
			 <doc:example>
		        <doc:source>
		            <svg data-view-box="{{ APP_VIEWPORT.viewBox }}"></svg>
		        </doc:source>
		    </doc:example>
		 */
		function () {
			'use strict';
			return {
				link: function (scope, element, attributes) {
					attributes.$observe('viewBox', function(value) {
						element.attr('viewBox', value);
					});
				}
			};
		}
	]);