jsgen: maps are always constructed using string keys

[gchumillas]

Describe the bug

Maps are always constructed using string keys, regardless of the original key type (which could be a number).

Reproduction Steps

Write a small main.v app:

fn map_keys[S, T](items map[S]T) []S {
	mut keys := []S{}
	for key, _ in items {
		keys << key
	}
	return keys
}

fn main() {
	items := {
		1: 'one'
		2: 'two'
		3: 'three'
	}

	JS.console.log(items)
	// As you can see, maps are constructed using the strings '1', '2', '3',
	// instead of the corresponding numbers.
	// {
	// 		map: { '1': { str: 'one' }, '2': { str: 'two' }, '3': { str: 'three' } },
	// 		length: 0
	// }

	// fails because maps are constructed using string keys, not number keys
	keys := map_keys(items)
	assert keys.contains(2)

}

Compile and execute it:

v -b js main.v
node main.js

Output:

{
  map: { '1': { str: 'one' }, '2': { str: 'two' }, '3': { str: 'three' } },
  length: 0
}
main.v:26: FAIL: fn main.main(): assert keys.contains(2)

Expected Behavior

The assertion should not fail.

Current Behavior

The assertion fails.

Possible Solution

No response

Additional Information/Context

No response

V version

V 0.4.10 d6a2a5e

Environment details (OS name and version, etc.)

V full version	V 0.4.10 52c7130.d6a2a5e
OS	macos, macOS, 15.5, 24F74
Processor	8 cpus, 64bit, little endian, Apple M1 Pro
Memory	0.56GB/16GB
V executable	/Users/gonzalo/Projects/Personal/vlang/v
V last modified time	2025-05-29 16:43:24
V home dir	OK, value: /Users/gonzalo/Projects/Personal/vlang
VMODULES	OK, value: /Users/gonzalo/.vmodules
VTMP	OK, value: /tmp/v_501
Current working dir	OK, value: /Users/gonzalo/Projects/Personal/vlang
Git version	git version 2.39.1
V git status	weekly.2025.22-13-gd6a2a5e9
.git/config present	true
cc version	Apple clang version 17.0.0 (clang-1700.0.13.5)
gcc version	Apple clang version 17.0.0 (clang-1700.0.13.5)
clang version	Apple clang version 17.0.0 (clang-1700.0.13.5)
tcc version	tcc version 0.9.28rc 2024-02-05 HEAD@105d70f7 (AArch64 Darwin)
tcc git status	thirdparty-macos-arm64 e447816c
emcc version	N/A
glibc version	N/A

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[huly-for-github]

Connected to Huly®: V_0.6-22968

[gchumillas]

Correction:

In JavaScript, map keys are always strings. When we write:

const m = { 1: 'one', 2: 'two', 3: 'three' }

We're actually writing:

const m = {'1': 'one', '2': 'two', '3': 'three'}

The JavaScript interpreter internally converts numbers to their equivalent strings.

[jorgeluismireles]

Seems javascript Objects require the keys to be strings. But javascript has maps where the keys are more diverse.