Many languages can be used for everything, including obscure languages like Smalltalk (see What makes a programming language “cool?”). The real question is whether JavaScript is used for everything in significant measure. You’ve pointed to IoT, but there are other languages that are heavily used for IoT such as C/C++, Python, Java, even Perl. By the way, Go is used in IoT, too. No one makes a big deal about that.

In mobile, Java/Kotlin (for Android) and Objective-C/Swift (for iOS) completely and utterly swamp JavaScript usage. It’s not even close.

In desktop, Java and C++ are still very heavily used. Electron gets a lot of hype that makes it appear to be a major competitor to Java and C++, but that’s misleading.

In backend services, Java, PHP, Go, Scala, and others are heavily used. Node is nowhere close to dominating in this area.

The “used everywhere” mantra is basically meaningless.

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