Frontend & browser·Modules, bundling and the build
you wrote `import` at the top of the file and the tooling could tell what you used without running anything.
ES module
Also calledESM, import syntax, static module
The standard module format, with static `import` and `export` declarations that can be analysed without executing the file. That static shape is what makes tree shaking possible at all, and it is why dynamic imports are the only conditional form allowed. Modules are strict mode, deferred, and evaluated once, which is why a module-level variable is a singleton whether you meant it to be or not.