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Set HTML5 video volume

Script to set the volume of <video> elements to 10%.

  1. // ==UserScript==
  2. // @name        Set HTML5 video volume
  3. // @description Script to set the volume of <video> elements to 10%.
  4. // @namespace   JeffersonScher
  5. // @author      Jefferson "jscher2000" Scher
  6. // @copyright   Copyright 2015 Jefferson Scher
  7. // @license     BSD
  8. // @include     *
  9. // @version     0.5
  10. // @grant       none
  11. // ==/UserScript==
  12.  
  13. var setvol_volumepct = 0.1; // Set volume to 10%
  14.  
  15. // == == == Detect added nodes / attach MutationObserver == == ==
  16. if (document.body){
  17.   // Check existing videos
  18.   setvol_checkNode(document.body);
  19.   // Watch for changes that could be new videos
  20.   var setvol_MutOb = (window.MutationObserver) ? window.MutationObserver : window.WebKitMutationObserver;
  21.   if (setvol_MutOb){
  22.     var setvol_chgMon = new setvol_MutOb(function(mutationSet){
  23.       mutationSet.forEach(function(mutation){
  24.         for (var setvol_node_count=0; setvol_node_count<mutation.addedNodes.length; setvol_node_count++){
  25.           if (mutation.addedNodes[setvol_node_count].nodeType == 1){
  26.             setvol_checkNode(mutation.addedNodes[setvol_node_count]);
  27.           }
  28.         }
  29.       });
  30.     });
  31.     // attach setvol_chgMon to document.body
  32.     var setvol_opts = {childList: true, subtree: true};
  33.     setvol_chgMon.observe(document.body, setvol_opts);
  34.   }
  35. }
  36.  
  37. function setvol_checkNode(el){
  38.   if (el.nodeName == "video") var vids = [el];
  39.   else var vids = el.querySelectorAll('video');
  40.   if (vids.length > 0){
  41.     for (var j=0; j<vids.length; j++){
  42.       vids[j].volume = setvol_volumepct;
  43.     }
  44.   }
  45. }