Add .if_exists()/.if_visible() (implements #266)

lib/actions.js

@@ -1063,6 +1063,20 @@ exports.exists = function(selector) {
 	});
 };
 
+/**
+ * Determine if the selector exists, at least once, on the page  and execute function if it does
+ * @param {string} [selector]
+ * @param {function} fn
+ */
+exports.if_exists = function(selector, fn) {
+	debug('.if_exists()', selector);
+	return this.count(selector).then(function(count) {
+		if (count > 0) {
+			return fn();
+                };
+	});
+};
+
 /**
  * Get the HTML for the page, or optionally for a selector.
  * @param {string} [selector]
@@ -1240,6 +1254,29 @@ exports.visible = function(selector) {
 		});
 };
 
+/**
+ * Determines if an element is visible and execute function if it is.
+ * @param {string} selector - The selector to find the visibility of.
+ * @param {function} fn
+ */
+exports.if_visible = function(selector, fn) {
+	debug('.if_visible()', selector);
+	return this
+		.__evaluate(function visible(selector) {
+			if (window.jQuery) {
+				return jQuery(selector).is(':visible');
+			} else {
+				var elem = document.querySelector(selector);
+				return elem && (elem.offsetWidth > 0 && elem.offsetHeight > 0);
+			}
+		}, selector)
+		.then(function(vis) {
+			if (vis) {
+				return fn();
+			};
+		});
+};
+
 /**
  * Log the output from either a previous chain method,
  * or a string the user passed in.