toastr: Add preventDuplicates

toastr/toastr-tests.ts

@@ -47,7 +47,8 @@ function test_fromdemo() {
 		toastr.options = {
 			debug: $('#debugInfo').prop('checked'),
 			tapToDismiss: $('#tapToDismiss').prop('checked'),
-			positionClass: $('#positionGroup input:radio:checked').val() || 'toast-top-right'
+			positionClass: $('#positionGroup input:radio:checked').val() || 'toast-top-right',
+			preventDuplicates: true
 		}
         if ($fadeIn.val().length) {
 			toastr.options.showDuration = +$fadeIn.val()

toastr/toastr.d.ts

@@ -114,6 +114,11 @@ interface ToastrOptions {
 	**/
 	newestOnTop?: boolean;
 
+    /**
+     * Rather than having identical toasts stack, set the preventDuplicates property to true. Duplicates are matched to the previous toast based on their message content.
+     */
+    preventDuplicates?: boolean;
+
 	/**
 	* Function to execute on toast click
 	*/