var u = "Browser";
        if (this.isIPad) {
            u = "iPad"
        } else {
            if (this.isDDGIgnore) {
                u = "Ignore"
            } else {
                if (/seamonkey/.test(x)) {
                    u = "SeaMonkey"
                } else {
                    if (/iceape/.test(x)) {
                        u = "Iceape"
                    } else {
                        if (/palemoon/.test(x)) {
                            u = "PaleMoon"
                        } else {
                            if (this.isFirefox) {
                                u = "Firefox"
                            } else {
                                if (this.isAndroid) {
                                    u = "Android"
                                } else {
                                    if (/xbox/.test(x)) {
                                        u = "xBox"
                                    } else {
                                        if (/midori/.test(x)) {
                                            u = "Midori"
                                        } else {
                                            if (/opr/.test(x)) {
                                                u = "Opera"
                                            } else {
                                                if (/maxthon/.test(x)) {
                                                    u = "Maxthon"
                                                } else {
                                                    if (this.isYandex) {
                                                        u = "Yandex"
                                                    } else {
                                                        if (/vivaldi/.test(x)) {
                                                            u = "Vivaldi"
                                                        } else {
                                                            if (this.isChrome) {
                                                                u = "Chrome"
                                                            } else {
                                                                if (/fennec/.test(x)) {
                                                                    u = "Fennec"
                                                                } else {
                                                                    if (/epiphany/.test(x)) {
                                                                        u = "Epiphany"
                                                                    } else {
                                                                        if (this.isFirefox) {
                                                                            u = "Firefox"
                                                                        } else {
                                                                            if (/uzbl/.test(x)) {
                                                                                u = "Uzbl"
                                                                            } else {
                                                                                if (this.isEdge) {
                                                                                    u = "Edge"
                                                                                } else {
                                                                                    if (this.isIE && navigator.platform === "Win64" && !k() && Modernizr.touch && document.documentElement.clientWidth == screen.width) {
                                                                                        u = "IEMetro"
                                                                                    } else {
                                                                                        if (this.isIE) {
                                                                                            u = "IE"
                                                                                        } else {
                                                                                            if (this.isOpera) {
                                                                                                u = "Opera"
                                                                                            } else {
                                                                                                if (this.isIPhone) {
                                                                                                    u = "iPhone"
                                                                                                } else {
                                                                                                    if (/arora/.test(x)) {
                                                                                                        u = "Arora"
                                                                                                    } else {
                                                                                                        if (this.isSafari) {
                                                                                                            u = "Safari"
                                                                                                        } else {
                                                                                                            if (this.isKonqueror) {
                                                                                                                u = "Konqueror"
                                                                                                            } else {
                                                                                                                if (this.isBlackberry) {
                                                                                                                    u = "Blackberry"
                                                                                                                } else {
                                                                                                                    if (/phantomjs/.test(x)) {
                                                                                                                        u = "PhantomJS"
                                                                                                                    } else {
                                                                                                                        if (this.isIDevice) {
                                                                                                                            u = "iOS"
                                                                                                                        }
                                                                                                                    }
                                                                                                                }
                                                                                                            }
                                                                                                        }
                                                                                                    }
                                                                                                }
                                                                                            }
                                                                                        }
                                                                                    }
                                                                                }
                                                                            }
                                                                        }
                                                                    }
                                                                }
                                                            }
                                                        }
                                                    }
                                                }
                                            }
                                        }
                                    }
                                }
                            }
                        }
                    }
                }
            }
        }

Found when looking at facebook.com code and formatting using google chrome developer tools.

By jcubic, 2017-01-03 18:38:30