diff --git a/TODO b/TODO
index 65dc079..3d0851a 100644
--- a/TODO
+++ b/TODO
@@ -7,8 +7,6 @@ more information on demo page:
 
 page idx vs no
 tracking current page
-more js annoatation
-pdf:mobile device
 pdf:miui
 tmp dir: use pid
 remove page from dom -- UI option
diff --git a/share/pdf2htmlEX.js.in b/share/pdf2htmlEX.js.in
index 7522429..53cc561 100644
--- a/share/pdf2htmlEX.js.in
+++ b/share/pdf2htmlEX.js.in
@@ -73,6 +73,9 @@ var EPS = 1e-6;
 
 /************************************/
 /* utility function */
+/**
+ * @param{Array.<number>} ctm
+ */
 function invert(ctm) {
   var det = ctm[0] * ctm[3] - ctm[1] * ctm[2];
   return [ ctm[3] / det
@@ -83,6 +86,10 @@ function invert(ctm) {
           ,(ctm[1] * ctm[4] - ctm[0] * ctm[5]) / det
         ];
 };
+/**
+ * @param{Array.<number>} ctm
+ * @param{Array.<number>} pos
+ */
 function transform(ctm, pos) {
   return [ctm[0] * pos[0] + ctm[2] * pos[1] + ctm[4]
          ,ctm[1] * pos[0] + ctm[3] * pos[1] + ctm[5]];
@@ -175,6 +182,9 @@ Page.prototype = {
       this.shown = true;
     }
   },
+  /**
+   * @param{number} ratio
+   */
   rescale : function(ratio) {
     if(ratio == 0) {
       // reset scale
@@ -234,9 +244,10 @@ Page.prototype = {
 /** 
  * export pdf2htmlEX.Viewer
  * @constructor
+ * @param{Object=} config
  */
 function Viewer(config) {
-  this.config = clone_and_extend_objs(DEFAULT_CONFIG, config);
+  this.config = clone_and_extend_objs(DEFAULT_CONFIG, (arguments.length > 0 ? config : {}));
   this.pages_loading = [];
   this.init_before_loading_content();
 
@@ -446,8 +457,8 @@ Viewer.prototype = {
     }
   },
 
-  /*
-   * renew: renew the existing schedule instead of using the old one
+  /**
+   * @param{boolean} renew renew the existing schedule instead of using the old one
    */
   schedule_render : function(renew) {
     if(this.render_timer !== undefined) {
@@ -663,6 +674,9 @@ Viewer.prototype = {
     return null;
   },
 
+  /**
+   * @param{Event} e
+   */
   link_handler : function (e) {
     var target = e.target;
 
@@ -762,7 +776,7 @@ Viewer.prototype = {
 
   /**
    * @param{number} page_idx
-   * @param{Array=} pos [x,y] in UNSCALED COORDINATION, where (0,0) is the top-left corner
+   * @param{Array.<number>=} pos [x,y] in UNSCALED COORDINATION, where (0,0) is the top-left corner
    */
   scroll_to : function(page_idx, pos) {
     var target_page = this.pages[page_idx];