The Window.navigator read-only property returns a reference to the Navigator object, which can be queried for information about the application running the script.
Syntax
navigatorObject = window.navigator
Examples
Example #1: Browser detect and return a string
var sBrowser, sUsrAg = navigator.userAgent;
if(sUsrAg.indexOf("Chrome") > -1) {
    sBrowser = "Google Chrome";
} else if (sUsrAg.indexOf("Safari") > -1) {
    sBrowser = "Apple Safari";
} else if (sUsrAg.indexOf("Opera") > -1) {
    sBrowser = "Opera";
} else if (sUsrAg.indexOf("Firefox") > -1) {
    sBrowser = "Mozilla Firefox";
} else if (sUsrAg.indexOf("MSIE") > -1) {
    sBrowser = "Microsoft Internet Explorer";
}
alert("You are using: " + sBrowser);
Example #2: Browser detect and return an index
function getBrowserId () {
    var
        aKeys = ["MSIE", "Firefox", "Safari", "Chrome", "Opera"],
        sUsrAg = navigator.userAgent, nIdx = aKeys.length - 1;
    for (nIdx; nIdx > -1 && sUsrAg.indexOf(aKeys[nIdx]) === -1; nIdx--);
    return nIdx
}
console.log(getBrowserId());
Specification
- HTML5
 The definition of 'window.navigator' in that specification.
- HTML5.1
 The definition of 'window.navigator' in that specification.
- WHATWG HTML Living Standard
 The definition of 'window.navigator' in that specification.
See also
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