BOM对象

1 BOM

浏览器对象模型
BOM为我们提供了一组对象，通过这组对象可以完成对浏览器的各种操作
BOM对象：
- Window —— 代表浏览器窗口（全局对象）
- Navigator —— 浏览器的对象（可以用来识别浏览器）
- Location —— 浏览器的地址栏信息
- History —— 浏览器的历史记录（控制浏览器前进后退）
- Screen —— 屏幕的信息
BOM对象都是作为window对象的属性保存的，所以可以直接在JS中访问这些对象

2 navigator

Navigator —— 浏览器的对象（可以用来识别浏览器）

userAgent 返回一个用来描述浏览器信息的字符串

获取用户当前的浏览器信息

let sBrowser
const sUsrAg = navigator.userAgent

// The order matters here, and this may report false positives for unlisted browsers.

if (sUsrAg.indexOf("Firefox") > -1) {
    sBrowser = "Mozilla Firefox"
    // "Mozilla/0 (X11; Ubuntu; Linux x86_64; rv:61.0) Gecko/20100101 Firefox/61.0"
} else if (sUsrAg.indexOf("SamsungBrowser") > -1) {
    sBrowser = "Samsung Internet"
    // "Mozilla/0 (Linux; Android 9; SAMSUNG SM-G955F Build/PPR1.180610.011) AppleWebKit/537.36 (KHTML, like Gecko) SamsungBrowser/9.4 Chrome/67.0.3396.87 Mobile Safari/537.36
} else if (
    sUsrAg.indexOf("Opera") > -1 ||
    sUsrAg.indexOf("OPR") > -1
) {
    sBrowser = "Opera"
    // "Mozilla/0 (Macintosh; Intel Mac OS X 10_14_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.102 Safari/537.36 OPR/57.0.3098.106"
} else if (sUsrAg.indexOf("Trident") > -1) {
    sBrowser = "Microsoft Internet Explorer"
    // "Mozilla/0 (Windows NT 10.0; WOW64; Trident/7.0; .NET4.0C; .NET4.0E; Zoom 3.6.0; wbx 1.0.0; rv:11.0) like Gecko"
} else if (sUsrAg.indexOf("Edge") > -1) {
    sBrowser = "Microsoft Edge (Legacy)"
    // "Mozilla/0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.36 Edge/16.16299"
} else if (sUsrAg.indexOf("Edg") > -1) {
    sBrowser = "Microsoft Edge (Chromium)"
    // Mozilla/0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.124 Safari/537.36 Edg/91.0.864.64
} else if (sUsrAg.indexOf("Chrome") > -1) {
    sBrowser = "Google Chrome or Chromium"
    // "Mozilla/0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Ubuntu Chromium/66.0.3359.181 Chrome/66.0.3359.181 Safari/537.36"
} else if (sUsrAg.indexOf("Safari") > -1) {
    sBrowser = "Apple Safari"
    // "Mozilla/0 (iPhone; CPU iPhone OS 11_4 like Mac OS X) AppleWebKit/601.15 (KHTML, like Gecko) Version/11.0 Mobile/15E148 Safari/604.1 980x1306"
} else {
    sBrowser = "unknown"
}

alert(`You are using: ${sBrowser}`)