Detect Internet Explorer in JavaScript

This JavaScript function returns true if the user is using Internet Explorer, and it returns false otherwise:

const usingInternetExplorer = () => {
    return (navigator.userAgent.indexOf(`MSIE `) > - 1 || navigator.userAgent.indexOf(`Trident/`) > - 1);
};

In the below example, the usingInternetExplorer() function is called inside a conditional statement:

if (!!usingInternetExplorer()) {
    // The user is using Internet Explorer!
} else {
    // The user is NOT using Internet Explorer!
}

Older versions of Internet Explorer include "MSIE " in the user agent string, while newer versions contain "Trident/".

But please remember that these user agent strings can be easily faked!

By the way, here’s a quick one-liner alternative with the exact same behavior, if you need it:

const usingInternetExplorer = () => (navigator.userAgent.indexOf(`MSIE `) > - 1 || navigator.userAgent.indexOf(`Trident/`) > - 1);

Conclusion

I’m sure we’ll never know why Internet Explorer changed its user agent string to be less easily recognizable…

Anyway, I hope this helped you out!