I read a book calls 'Professional Javascript For Web Developers 2nd edition' and it state that this code can detect browser rendering engine:
<script type="text/javascript">
var client = function(){
var engine = {
ie: 0,
gecko: 0,
webkit: 0,
khtml: 0,
opera: 0,
ver: null
};
return {
engine : engine
};
}();
if(client.engine.ie){
alert("This is internet explorer");
}else if(client.engine.gecko > 1.5){
if(client.engine.ver == "1.8.1"){
alert("This is gecko rendering browser");
}
}else if(client.engine.webkit){
alert("This is web kit");
}else if(client.engine.khtml){
alert("This is khtml");
}else{
alert("none of the above");
}
</script>
but it seems like doesn't work, so how this code work to detect browser rendering engine?Thanks
If you read the rest of the chapter and download the source
then you can look at client.js:
It still works in IE10 on win7 and Chrome 67 on Win10
It needs a little change to handle IE11 (Trident/) and Edge(Edge/) - see later
var client = function() {
//rendering engines
var engine = {
ie: 0,
gecko: 0,
webkit: 0,
khtml: 0,
opera: 0,
//complete version
ver: null
};
//browsers
var browser = {
//browsers
ie: 0,
firefox: 0,
safari: 0,
konq: 0,
opera: 0,
chrome: 0,
safari: 0,
//specific version
ver: null
};
//platform/device/OS
var system = {
win: false,
mac: false,
x11: false,
//mobile devices
iphone: false,
ipod: false,
nokiaN: false,
winMobile: false,
macMobile: false,
//game systems
wii: false,
ps: false
};
//detect rendering engines/browsers
var ua = navigator.userAgent;
if (window.opera) {
engine.ver = browser.ver = window.opera.version();
engine.opera = browser.opera = parseFloat(engine.ver);
} else if (/AppleWebKit\/(\S+)/.test(ua)) {
engine.ver = RegExp["$1"];
engine.webkit = parseFloat(engine.ver);
//figure out if it's Chrome or Safari
if (/Chrome\/(\S+)/.test(ua)) {
browser.ver = RegExp["$1"];
browser.chrome = parseFloat(browser.ver);
} else if (/Version\/(\S+)/.test(ua)) {
browser.ver = RegExp["$1"];
browser.safari = parseFloat(browser.ver);
} else {
//approximate version
var safariVersion = 1;
if (engine.webkit < 100) {
safariVersion = 1;
} else if (engine.webkit < 312) {
safariVersion = 1.2;
} else if (engine.webkit < 412) {
safariVersion = 1.3;
} else {
safariVersion = 2;
}
browser.safari = browser.ver = safariVersion;
}
} else if (/KHTML\/(\S+)/.test(ua) || /Konqueror\/([^;]+)/.test(ua)) {
engine.ver = browser.ver = RegExp["$1"];
engine.khtml = browser.konq = parseFloat(engine.ver);
} else if (/rv:([^\)]+)\) Gecko\/\d{8}/.test(ua)) {
engine.ver = RegExp["$1"];
engine.gecko = parseFloat(engine.ver);
//determine if it's Firefox
if (/Firefox\/(\S+)/.test(ua)) {
browser.ver = RegExp["$1"];
browser.firefox = parseFloat(browser.ver);
}
} else if (/MSIE ([^;]+)/.test(ua)) { // add Trident/ to test IE11, Edge for Edge
engine.ver = browser.ver = RegExp["$1"];
engine.ie = browser.ie = parseFloat(engine.ver);
}
//detect browsers
browser.ie = engine.ie;
browser.opera = engine.opera;
//detect platform
var p = navigator.platform;
system.win = p.indexOf("Win") == 0;
system.mac = p.indexOf("Mac") == 0;
system.x11 = (p == "X11") || (p.indexOf("Linux") == 0);
//detect windows operating systems
if (system.win) {
if (/Win(?:dows )?([^do]{2})\s?(\d+\.\d+)?/.test(ua)) {
if (RegExp["$1"] == "NT") {
switch (RegExp["$2"]) {
case "5.0":
system.win = "2000";
break;
case "5.1":
system.win = "XP";
break;
case "6.0":
system.win = "Vista";
break;
default:
system.win = "NT";
break;
}
} else if (RegExp["$1"] == "9x") {
system.win = "ME";
} else {
system.win = RegExp["$1"];
}
}
}
//mobile devices
system.iphone = ua.indexOf("iPhone") > -1;
system.ipod = ua.indexOf("iPod") > -1;
system.nokiaN = ua.indexOf("NokiaN") > -1;
system.winMobile = (system.win == "CE");
system.macMobile = (system.iphone || system.ipod);
//gaming systems
system.wii = ua.indexOf("Wii") > -1;
system.ps = /playstation/i.test(ua);
//return it
return {
engine: engine,
browser: browser,
system: system
};
}();
console.log(client.browser,client.engine,client.system)It needs a little change to handle IE11 (Trident/) and Edge(Edge/)
var client = function() {
//rendering engines
var engine = {
ie: 0,
edge: 0,
gecko: 0,
webkit: 0,
khtml: 0,
opera: 0,
//complete version
ver: null
};
//browsers
var browser = {
//browsers
ie: 0,
edge: 0,
firefox: 0,
safari: 0,
konq: 0,
opera: 0,
chrome: 0,
safari: 0,
//specific version
ver: null
};
//platform/device/OS
var system = {
win: false,
mac: false,
x11: false,
//mobile devices
iphone: false,
ipod: false,
nokiaN: false,
winMobile: false,
macMobile: false,
//game systems
wii: false,
ps: false
};
//detect rendering engines/browsers
var ua = navigator.userAgent;
if (window.opera) {
engine.ver = browser.ver = window.opera.version();
engine.opera = browser.opera = parseFloat(engine.ver);
}
else if (/Edge\/([^;]+)/.test(ua)) { // IE11
engine.ver = browser.ver = RegExp["$1"];
engine.edge = browser.edge = parseFloat(engine.ver);
} else if (/AppleWebKit\/(\S+)/.test(ua)) {
engine.ver = RegExp["$1"];
engine.webkit = parseFloat(engine.ver);
//figure out if it's Chrome or Safari
if (/Chrome\/(\S+)/.test(ua)) {
browser.ver = RegExp["$1"];
browser.chrome = parseFloat(browser.ver);
} else if (/Version\/(\S+)/.test(ua)) {
browser.ver = RegExp["$1"];
browser.safari = parseFloat(browser.ver);
} else {
//approximate version
var safariVersion = 1;
if (engine.webkit < 100) {
safariVersion = 1;
} else if (engine.webkit < 312) {
safariVersion = 1.2;
} else if (engine.webkit < 412) {
safariVersion = 1.3;
} else {
safariVersion = 2;
}
browser.safari = browser.ver = safariVersion;
}
} else if (/KHTML\/(\S+)/.test(ua) || /Konqueror\/([^;]+)/.test(ua)) {
engine.ver = browser.ver = RegExp["$1"];
engine.khtml = browser.konq = parseFloat(engine.ver);
} else if (/rv:([^\)]+)\) Gecko\/\d{8}/.test(ua)) {
engine.ver = RegExp["$1"];
engine.gecko = parseFloat(engine.ver);
//determine if it's Firefox
if (/Firefox\/(\S+)/.test(ua)) {
browser.ver = RegExp["$1"];
browser.firefox = parseFloat(browser.ver);
}
} else if (/MSIE ([^;]+)/.test(ua)) { // IE <= 10
engine.ver = browser.ver = RegExp["$1"];
engine.ie = browser.ie = parseFloat(engine.ver);
} else if (/Trident\/([^;]+)/.test(ua)) { // IE11
engine.ver = RegExp["$1"];
browser.ver = parseFloat(ua.split("rv:")[1]);
engine.ie = parseFloat(browser.ver);
}
//detect browsers
browser.ie = engine.ie;
browser.opera = engine.opera;
//detect platform
var p = navigator.platform;
system.win = p.indexOf("Win") == 0;
system.mac = p.indexOf("Mac") == 0;
system.x11 = (p == "X11") || (p.indexOf("Linux") == 0);
//detect windows operating systems
if (system.win) {
if (/Win(?:dows )?([^do]{2})\s?(\d+\.\d+)?/.test(ua)) {
if (RegExp["$1"] == "NT") {
switch (RegExp["$2"]) {
case "5.0":
system.win = "2000";
break;
case "5.1":
system.win = "XP";
break;
case "6.0":
system.win = "Vista";
break;
default:
system.win = "NT";
break;
}
} else if (RegExp["$1"] == "9x") {
system.win = "ME";
} else {
system.win = RegExp["$1"];
}
}
}
//mobile devices
system.iphone = ua.indexOf("iPhone") > -1;
system.ipod = ua.indexOf("iPod") > -1;
system.nokiaN = ua.indexOf("NokiaN") > -1;
system.winMobile = (system.win == "CE");
system.macMobile = (system.iphone || system.ipod);
//gaming systems
system.wii = ua.indexOf("Wii") > -1;
system.ps = /playstation/i.test(ua);
//return it
return {
engine: engine,
browser: browser,
system: system
};
}();
console.log(JSON.stringify({ browser:client.browser,engine:client.engine,system:client.system},null, 2));The script obviously doesn't work - it just sets a bunch of variables to zero or null and then checks if they're zero or null. My guess would be that this is not the whole script, and that the crucial part is missing.
What one would normally do is read the UserAgent string (I'm too lazy to google how exactly you do that) and throw some regular expressions at it to detect known patterns. This kind of user agent sniffing has a bunch of downsides though:
It's not forward compatible. You don't know which UA strings future browsers are going to use, so most likely, newer browsers will fail your test and receive the most stripped-down version, even though they could easily handle the full-eye-candy-blow-your-mind one.
The UA string isn't reliable. Just because so many websites make the mistake of sniffing, and then not getting updated regularly, users set different UA strings, purposefully reporting a "wrong" render engine. And then they forget to switch it back, causing all sorts of weird behaviour.
Just because someone has a certain render engine doesn't mean you can rely on all features being there. Browsers are highly configurable, and people use all sorts of extensions, blocking things selectively or completely.
Long story short, instead of sniffing the UA string and assuming things are what you think they are, just test features individually and directly.
This is just an alternative. If you are really worried about the rendering issue, you can always playground with the screen width, as far as design is concerned.
For Single Page applications, you just need to screen the screen to the correct sizes depending upon the screen width and your requirement... :)
We made use of:
if(screen.width > 360 && screen.width < 720){
document.write ('<meta name="viewport" content="initial-scale=.25, maximum-scale=.25, user-scalable=no">');
}
For ios, iphone, ipad it's quite easy as you have to play with just fixed sizes or the standard sizes.
For Android, really frustates you, what we found good was to move ahead with the ldpi, mdpi, hdpi, xhdi and max xxhdpi (for tabs) Pixel ranges.
来源：https://stackoverflow.com/questions/6189216/how-to-detect-browser-rendering-engine-in-javascript