The updates (assignments, increments and decrements) of imported bindings by ES Modules cause runtime errors. The standard import looks something like import something from 'somewhere/else';. But what if the module you are importing isn’t actually exporting anything and only used to run code? As you move into modules, you will find at first side-effects are going to happen. The import statement isn't a pass-by-value situation. You will get a binding to the original source.

Bad Practice

import mod, { named } from "./mod.mjs"
import * as mod_ns from "./mod.mjs"

mod++            // ERROR: 'mod' is readonly.
named++          // ERROR: 'named' is readonly.
mod_ns.named = 3 // ERROR: the members of 'mod_ns' is readonly.
mod_ns = {}      // ERROR: 'mod_ns' is readonly.

Recommended

import mod, { named } from "./mod.mjs"
import * as mod_ns from "./mod.mjs"

mod.prop = 1
named.prop = 2
mod_ns.named.prop = 3

// Known Limitation
function test(obj) {
    obj.named = 4 // Not errored because 'obj' is not namespace objects.
}
test(mod_ns) // Not errored because it doesn't know that 'test' updates the member of the argument.

Spelunking-Studios / The-Caverns-Website

No ignore rules found