在 YouTube 页面添加双语字幕，支持双语字幕下载
// ==UserScript==
// @name YouTube 双语字幕下载 / YouTube Biligual Subtitles Downloader
// @namespace https://github.com/Nehemiab/YouTube-Biligual-Subtitles-Downloader
// @version 1.0
// @description 在 YouTube 页面添加双语字幕，支持双语字幕下载
// @author NEHEMIAB
// @match *://www.youtube.com/watch?v=*
// @match *://www.youtube.com
// @match *://www.youtube.com/*
// @grant none
// @run-at document-start
// @icon https://www.google.com/s2/favicons?sz=64&domain=youtube.com
// @run-at document-end
// @copyright 2025,NEHEMIAB(https://github.com/Nehemiab/YouTube-Biligual-Subtitles-Downloader)
// @license MIT
// @thanks Coink,Claude
// ==/UserScript==
(function() {
// 全局变量储存处理后的字幕数据
let ytSubtitleData = null;
function hookit(){
(function(global, factory) {
// 将工厂函数的所有导出赋给全局对象
for (var key in factory) {
global[key] = factory[key];
}
})(window, (function() {
'use strict';
// 支持的XHR事件类型
var events = ['load', 'loadend', 'timeout', 'error', 'readystatechange', 'abort'];
var XHR_PROXY_KEY = '__xhr';
/**
* 配置事件对象
* @param {Event} event - 原始事件对象
* @param {Object} target - 事件的目标对象
* @return {Event} 配置好的事件对象
*/
function configEvent(event, target) {
var eventCopy = {};
for (var key in event) {
eventCopy[key] = event[key];
}
eventCopy.target = eventCopy.currentTarget = target;
return eventCopy;
}
/**
* 钩住XMLHttpRequest
* @param {Object} hooks - 包含各种钩子的对象
* @param {Window} win - window对象，默认为全局window
* @return {Function} 修改后的XMLHttpRequest构造函数
*/
function hook(hooks, win) {
win = win || window;
// 保存原始的XMLHttpRequest
win[XHR_PROXY_KEY] = win[XHR_PROXY_KEY] || win.XMLHttpRequest;
// 创建新的XMLHttpRequest构造函数
win.XMLHttpRequest = function() {
var xhr = new win[XHR_PROXY_KEY]();
// 确保所有事件处理程序属性存在
for (var i = 0; i < events.length; ++i) {
var eventName = 'on' + events[i];
if (xhr[eventName] === undefined) {
xhr[eventName] = null;
}
}
// 为每个属性和方法创建代理
for (var prop in xhr) {
var type = '';
try {
type = typeof xhr[prop];
} catch(e) { }
if (type === 'function') {
// 代理方法
this[prop] = createMethodProxy(prop);
} else {
// 代理属性
Object.defineProperty(this, prop, {
get: createGetter(prop),
set: createSetter(prop),
enumerable: true
});
}
}
var self = this;
xhr.getProxy = function() { return self; };
this.xhr = xhr;
};
// 复制XMLHttpRequest的静态属性
Object.assign(win.XMLHttpRequest, {
UNSENT: 0,
OPENED: 1,
HEADERS_RECEIVED: 2,
LOADING: 3,
DONE: 4
});
/**
* 创建属性getter代理
*/
function createGetter(prop) {
return function() {
var value = this.hasOwnProperty(prop + '_') ?
this[prop + '_'] : this.xhr[prop];
var getter = (hooks[prop] || {}).getter;
return getter && getter(value, this) || value;
};
}
/**
* 创建属性setter代理
*/
function createSetter(prop) {
return function(value) {
var xhr = this.xhr;
var self = this;
var hook = hooks[prop];
if (prop.substring(0, 2) === 'on') {
// 事件处理程序
self[prop + '_'] = value;
xhr[prop] = function(e) {
e = configEvent(e, self);
if (hook && hook.call(self, xhr, e)) {
return;
}
value.call(self, e);
};
} else {
// 常规属性
var setter = (hook || {}).setter;
value = setter && setter(value, self) || value;
this[prop + '_'] = value;
try {
xhr[prop] = value;
} catch(e) { }
}
};
}
/**
* 创建方法代理
*/
function createMethodProxy(method) {
return function() {
var args = [].slice.call(arguments);
var hook = hooks[method];
if (hook) {
var result = hook.call(this, args, this.xhr);
if (result) {
return result;
}
}
return this.xhr[method].apply(this.xhr, args);
};
}
return win.XMLHttpRequest;
}
/**
* 解除钩子
* @param {Window} win - window对象，默认为全局window
*/
function unHook(win) {
win = win || window;
if (win[XHR_PROXY_KEY]) {
win.XMLHttpRequest = win[XHR_PROXY_KEY];
}
win[XHR_PROXY_KEY] = undefined;
}
/**
* 代理XHR请求
*/
function proxy(options, win) {
if (win = win || window, win.__xhr) {
throw "Ajax is already hooked.";
}
return proxyXhr(options, win);
}
/**
* 解除代理
*/
function unProxy(win) {
unHook(win);
}
/**
* 创建XHR代理
*/
function proxyXhr(options, win) {
var onRequest = options.onRequest;
var onResponse = options.onResponse;
var onError = options.onError;
return hook({
// 处理事件
onload: returnTrue,
onloadend: returnTrue,
onerror: createErrorHandler('error'),
ontimeout: createErrorHandler('timeout'),
onabort: createErrorHandler('abort'),
onreadystatechange: function(xhr) {
if (xhr.readyState === 4 && xhr.status !== 0) {
handleResponse(xhr, this);
} else if (xhr.readyState !== 4) {
triggerEvent(xhr, 'readystatechange');
}
return true;
},
// 处理方法
open: function(args, xhr) {
var self = this;
var config = xhr.config = { headers: {} };
config.method = args[0];
config.url = args[1];
config.async = args[2];
config.user = args[3];
config.password = args[4];
config.xhr = xhr;
var eventName = 'onreadystatechange';
if (!xhr[eventName]) {
xhr[eventName] = function() {
return handleReadyStateChange(xhr, self);
};
}
if (onRequest) return true;
},
send: function(args, xhr) {
var config = xhr.config;
config.withCredentials = xhr.withCredentials;
config.body = args[0];
if (onRequest) {
var callback = function() {
onRequest(config, new RequestHandler(xhr));
};
if (config.async === false) {
callback();
} else {
setTimeout(callback);
}
return true;
}
},
setRequestHeader: function(args, xhr) {
xhr.config.headers[args[0].toLowerCase()] = args[1];
if (onRequest) return true;
},
addEventListener: function(args, xhr) {
var self = this;
if (events.indexOf(args[0]) !== -1) {
var listener = args[1];
getWatcher(xhr).addEventListener(args[0], function(e) {
var event = configEvent(e, self);
event.type = args[0];
event.isTrusted = true;
listener.call(self, event);
});
return true;
}
},
getAllResponseHeaders: function(args, xhr) {
var headers = xhr.resHeader;
if (headers) {
var result = '';
for (var key in headers) {
result += key + ': ' + headers[key] + '\r\n';
}
return result;
}
},
getResponseHeader: function(args, xhr) {
var headers = xhr.resHeader;
if (headers) {
return headers[(args[0] || '').toLowerCase()];
}
}
}, win);
/**
* 处理响应
*/
function handleResponse(xhr, xhrProxy) {
var response = {
response: xhrProxy.response || xhrProxy.responseText,
status: xhrProxy.status,
statusText: xhrProxy.statusText,
config: xhr.config,
headers: xhr.resHeader || parseHeaders(xhrProxy.getAllResponseHeaders())
};
if (!onResponse) {
new ResponseHandler(xhr).resolve(response);
return;
}
onResponse(response, new ResponseHandler(xhr));
}
/**
* 处理错误
*/
function createErrorHandler(type) {
return function(xhr, e) {
handleError(xhr, this, e, type);
return true;
};
}
function handleError(xhr, xhrProxy, error, type) {
var errorObject = {
config: xhr.config,
error: error,
type: type
};
var handler = new ErrorHandler(xhr);
if (onError) {
onError(errorObject, handler);
} else {
handler.next(errorObject);
}
}
function handleReadyStateChange(xhr, xhrProxy) {
return xhr.readyState === 4 && xhr.status !== 0 ?
handleResponse(xhr, xhrProxy) :
xhr.readyState !== 4 && triggerEvent(xhr, 'readystatechange');
}
function returnTrue() {
return true;
}
}
// 辅助函数
function trim(str) {
return str.replace(/^\s+|\s+$/g, '');
}
function getWatcher(xhr) {
return xhr.watcher || (xhr.watcher = document.createElement('a'));
}
function triggerEvent(xhr, type) {
var xhrProxy = xhr.getProxy();
var eventKey = 'on' + type + '_';
var event = configEvent({ type: type }, xhrProxy);
if (xhrProxy[eventKey]) {
xhrProxy[eventKey](event);
}
var customEvent;
if (typeof Event === 'function') {
customEvent = new Event(type, { bubbles: false });
} else {
customEvent = document.createEvent('Event');
customEvent.initEvent(type, false, true);
}
getWatcher(xhr).dispatchEvent(customEvent);
}
function parseHeaders(headerString) {
return headerString.split('\r\n').reduce(function(headers, line) {
if (line === '') return headers;
var parts = line.split(':');
var key = parts.shift();
var value = trim(parts.join(':'));
headers[key] = value;
return headers;
}, {});
}
// Handler类实现
var PROTO = 'prototype';
// 基础Handler
function Handler(xhr) {
this.xhr = xhr;
this.xhrProxy = xhr.getProxy();
}
Handler[PROTO] = Object.create({
resolve: function(response) {
var xhrProxy = this.xhrProxy;
var xhr = this.xhr;
xhrProxy.readyState = 4;
xhr.resHeader = response.headers;
xhrProxy.response = xhrProxy.responseText = response.response;
xhrProxy.statusText = response.statusText;
xhrProxy.status = response.status;
triggerEvent(xhr, 'readystatechange');
triggerEvent(xhr, 'load');
triggerEvent(xhr, 'loadend');
},
reject: function(error) {
this.xhrProxy.status = 0;
triggerEvent(this.xhr, error.type);
triggerEvent(this.xhr, 'loadend');
}
});
// 创建链式Handler工厂
function createHandler(nextHandler) {
function ChainedHandler(xhr) {
Handler.call(this, xhr);
}
ChainedHandler[PROTO] = Object.create(Handler[PROTO]);
ChainedHandler[PROTO].next = nextHandler;
return ChainedHandler;
}
// 具体的Handler实现
var RequestHandler = createHandler(function(config) {
var xhr = this.xhr;
config = config || xhr.config;
xhr.withCredentials = config.withCredentials;
xhr.open(config.method, config.url, config.async !== false, config.user, config.password);
for (var key in config.headers) {
xhr.setRequestHeader(key, config.headers[key]);
}
xhr.send(config.body);
});
var ResponseHandler = createHandler(function(response) {
this.resolve(response);
});
var ErrorHandler = createHandler(function(error) {
this.reject(error);
});
// 导出API
return {
ah: {
proxy: proxy,
unProxy: unProxy,
hook: hook,
unHook: unHook
}
};
})());
let localeLang = document.documentElement.lang || navigator.language || 'en' // follow the language used in YouTube Page
// localeLang = 'zh' // uncomment this line to define the language you wish here
ah.proxy({
onRequest: (config, handler) => {
handler.next(config);
},
onResponse: (response, handler) => {
if (response.config.url.includes('/api/timedtext') && !response.config.url.includes('&translate_h00ked')) {
let xhr = new XMLHttpRequest();
// Use RegExp to clean '&tlang=...' in our xhr request params while using Y2B auto translate.
let url = response.config.url
url = url.replace(/(^|[&?])tlang=[^&]*/g, '')
url = `${url}&tlang=${localeLang}&translate_h00ked`
xhr.open('GET', url, false);
xhr.send();
let defaultJson = null
if (response.response) {
const jsonResponse = JSON.parse(response.response)
if (jsonResponse.events) defaultJson = jsonResponse
}
const localeJson = JSON.parse(xhr.response)
let isOfficialSub = true;
for (const defaultJsonEvent of defaultJson.events) {
if (defaultJsonEvent.segs && defaultJsonEvent.segs.length > 1) {
isOfficialSub = false;
break;
}
}
// Merge default subs with locale language subs
if (isOfficialSub) {
// when length of segments are the same
for (let i = 0, len = defaultJson.events.length; i < len; i++) {
const defaultJsonEvent = defaultJson.events[i]
if (!defaultJsonEvent.segs) continue
const localeJsonEvent = localeJson.events[i]
if (`${defaultJsonEvent.segs[0].utf8}`.trim() !== `${localeJsonEvent.segs[0].utf8}`.trim()) {
// avoid merge subs while the are the same
defaultJsonEvent.segs[0].utf8 += ('\n' + localeJsonEvent.segs[0].utf8)
}
}
} else {
// when length of segments are not the same (e.g. automatic generated english subs)
let pureLocalEvents = localeJson.events.filter(event => event.aAppend !== 1 && event.segs)
for (const defaultJsonEvent of defaultJson.events) {
if (!defaultJsonEvent.segs) continue
let currentStart = defaultJsonEvent.tStartMs,
currentEnd = currentStart + defaultJsonEvent.dDurationMs
let currentLocalEvents = pureLocalEvents.filter(pe => currentStart <= pe.tStartMs && pe.tStartMs < currentEnd)
let localLine = ''
for (const ev of currentLocalEvents) {
for (const seg of ev.segs) {
localLine += seg.utf8
}
localLine += ''; // add ZWSP to avoid words stick together
}
let defaultLine = ''
for (const seg of defaultJsonEvent.segs) {
defaultLine += seg.utf8
}
defaultJsonEvent.segs[0].utf8 = defaultLine + '\n' + localLine
defaultJsonEvent.segs = [defaultJsonEvent.segs[0]]
}
}
ytSubtitleData = defaultJson;
response.response = JSON.stringify(defaultJson);
}
handler.resolve(response)
}
})
}
window.addEventListener('yt-navigate-finish', hookit)
window.addEventListener('load',function(){
if(this.window.location.href.includes('watch?v=')){
this.setTimeout(addDownloadButton, 1000)
}
}
)
function addDownloadButton() {
// 检查按钮是否已存在
if (document.getElementById('download-subtitle-btn')) return;
// 创建按钮元素
const downloadBtn = document.createElement('button');
downloadBtn.id = 'download-subtitle-btn';
downloadBtn.innerText = '下载字幕';
downloadBtn.style.cssText = `
background-color: orange;
color: white;
border: none;
border-radius: 3px;
padding: 5px 10px;
margin: 5px;
cursor: pointer;
font-weight: bold;
`;
downloadBtn.addEventListener('click', menu);
// 将按钮添加到up主信息旁边
const ownerElement = document.querySelector('#owner');
if (ownerElement) {
const customBtn = document.createElement('div');
customBtn.style.cssText = 'display: inline-block; margin-right: 10px;';
customBtn.appendChild(downloadBtn);
ownerElement.appendChild(customBtn, ownerElement.firstChild);
}
else {
// 备选方案，添加到视频上方
const videoContainer = document.querySelector('.html5-video-container');
if (videoContainer) {
const btnContainer = document.createElement('div');
btnContainer.style.cssText = 'position: absolute; top: 10px; left: 10px; z-index: 1000;';
btnContainer.appendChild(downloadBtn);
videoContainer.parentNode.insertBefore(btnContainer, videoContainer);
}
}
}
function menu() {
// 获取当前视频标题
const videoTitle = document.querySelector('h1.ytd-watch-metadata')?.textContent?.trim() || 'youtube_subtitle';
if (ytSubtitleData && ytSubtitleData.events) {
// 转换为SRT格式
const srtContent = convertToSRT(ytSubtitleData.events);
// 创建下载链接
downloadSubtitle(srtContent, `${videoTitle}.srt`);
} else {
alert('请重启视频字幕，然后再尝试下载');
}
}
// 将YouTube字幕数据转换为SRT格式
function convertToSRT(events) {
let srtContent = '';
let index = 1;
for (const event of events) {
// 只处理有文字内容的事件
if (!event.segs || event.segs.length === 0) continue;
// 获取开始和结束时间
const startMs = event.tStartMs;
const endMs = startMs + event.dDurationMs;
// 获取文本内容
let text = '';
for (const seg of event.segs) {
if (seg.utf8) text += seg.utf8;
}
// 跳过空白字幕
if (!text.trim()) continue;
// 添加到SRT内容
srtContent += `${index}\n`;
srtContent += `${formatTime(startMs)} --> ${formatTime(endMs)}\n`;
srtContent += `${text}\n\n`;
index++;
}
return srtContent;
}
// 格式化毫秒时间为SRT时间格式 (00:00:00,000)
function formatTime(ms) {
const totalSeconds = Math.floor(ms / 1000);
const hours = Math.floor(totalSeconds / 3600);
const minutes = Math.floor((totalSeconds % 3600) / 60);
const seconds = totalSeconds % 60;
const milliseconds = Math.floor(ms % 1000);
return `${padZero(hours)}:${padZero(minutes)}:${padZero(seconds)},${padZero(milliseconds, 3)}`;
}
// 数字前补零
function padZero(num, length = 2) {
return num.toString().padStart(length, '0');
}
// 下载字幕文件
function downloadSubtitle(content, filename) {
const blob = new Blob([content], { type: 'text/plain;charset=utf-8' });
const url = URL.createObjectURL(blob);
const a = document.createElement('a');
a.href = url;
a.download = filename;
a.style.display = 'none';
document.body.appendChild(a);
a.click();
setTimeout(() => {
document.body.removeChild(a);
URL.revokeObjectURL(url);
}, 100);
}
})();