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Set HTML5 media player volume

Script to set the volume of <video> and <audio> elements to reduced value (defaults to 50%), with a menu item to change for the current page.

  1. // ==UserScript==
  2. // @name        Set HTML5 media player volume
  3. // @description Script to set the volume of <video> and <audio> elements to reduced value (defaults to 50%), with a menu item to change for the current page.
  4. // @namespace   JeffersonScher
  5. // @author      Jefferson "jscher2000" Scher
  6. // @copyright   Copyright 2017 Jefferson Scher
  7. // @license     BSD-3-clause
  8. // @include     *
  9. // @version     0.6
  10. // @grant       GM_registerMenuCommand
  11. // ==/UserScript==
  12.  
  13. var setvol_volumepct = 0.5; // Set volume to 50%
  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" || el.nodeName == "audio") var vids = [el];
  39.   else var vids = el.querySelectorAll('video, audio');
  40.   if (vids.length > 0){
  41.     for (var j=0; j<vids.length; j++){
  42.       vids[j].volume = setvol_volumepct;
  43.     }
  44.   }
  45. }
  46.  
  47. // This is not compatible with Greasemonkey 4, but should work in Tampermonkey and Violentmonkey
  48. function chgVol(e){
  49.   var newvol = prompt('Enter value between 0.0 and 1.0 for 0% to 100%', setvol_volumepct);
  50.   if (!isNaN(parseFloat(newvol))){
  51.     var newnum = parseFloat(newvol);
  52.     if (newnum < 0) newnum = 0;
  53.     if (newnum > 1) newnum = 1;
  54.     setvol_volumepct = newnum;
  55.     setvol_checkNode(document.body);
  56.   }
  57. }
  58. GM_registerMenuCommand('Change volume for this page', chgVol);