JavaScript arrow-function using navigator.userAgent as an example

Question

const browser = ((agent) => {
    switch (true) {
        case agent.indexOf("edge") > -1: return "edge";
        case agent.indexOf("edg") > -1: return "chromium based edge (dev or canary)";
        case agent.indexOf("opr") > -1 && !!window.opr: return "opera";
        case agent.indexOf("chrome") > -1 && !!window.chrome: return "chrome";
        case agent.indexOf("trident") > -1: return "ie";
        case agent.indexOf("firefox") > -1: return "firefox";
        case agent.indexOf("safari") > -1: return "safari";
    default: return "other";
    }
}) (window.navigator.userAgent.toLowerCase());

There is a simple example how to detect browser using navigator.userAgent property of Window object. Could someone explain what the latest line of this code actually does and why toLowerCase() method is necessary here?

Source

Do some research on [what an IIFE is](https://developer.mozilla.org/en-US/docs/Glossary/IIFE) and how they work. — Heretic Monkey, Nov 03 '20 at 14:43

score 1 · Accepted Answer · answered Nov 03 '20 at 14:44

End of the arrow function

End of the grouping operator that surrounds the arrow function

(...)

Calls the function, with arguments

window.navigator.userAgent.toLowerCase()

The argument

why toLowerCase() method is necessary here?

Because it is doing a case-insensitive comparison

JavaScript arrow-function using navigator.userAgent as an example

1 Answers1