Why JavaScript Is Neither Purely Interpreted nor Purely Compiled Today

I'm trying to understand how modern JavaScript engines execute code. V8, used by Chrome, Node.js, and other environments, parses JavaScript into an abstract syntax tree and then produces bytecode. Its interpreter, Ignition, can execute that bytecode so the program starts running quickly.

JavaScript was traditionally called an interpreted language because developers generally ran source code without compiling it ahead of time, and engines primarily executed it through interpretation. Modern engines also use just-in-time compilation: when code becomes "hot" through repeated execution, the engine can compile and optimize it into machine code that the CPU can run more directly.

Compiling everything immediately could improve later execution speed, but it would also increase startup time and memory usage, especially for code that runs only once or never runs. That seems to be why engines combine quick bytecode interpretation with selective runtime compilation.

Is this explanation accurate? Why was JavaScript historically classified as interpreted, and why is it more accurate to describe modern JavaScript execution as a combination of interpretation and JIT compilation?