Go source code is Unicode text encoded in UTF-8. (Source.)

GopherJS fails to process some unicode characters in Go code and emits JavaScript that does not print the correct characters.

I think it fails on "astral planes", or unicode characters that require more than 2 bytes using utf-8 encoding. But this is just a hypothesis from limited evidence/investigation.

Compare:

console.log("Hello, 世界. 😀!"); // U+1F600 emoji.

package main

import "fmt"

func main() {
    fmt.Println("Hello, 世界. 😀!") // U+1F600 emoji.
}

https://play.golang.org/p/M1rXP8bm6L

http://www.gopherjs.org/playground/

(You'll have to manually paste the code into GopherJS Playground. Due to the bug in GopherJS, the snippet cannot be loaded correctly.)

Thank you to @peggyl for the original report of this issue at https://gist.github.com/peggyl/72d47f6652d30a4f566a!

Relevant Reading

• http://www.fileformat.info/info/unicode/char/1f600/index.htm
• https://mathiasbynens.be/notes/javascript-unicode
• https://mathiasbynens.be/notes/javascript-escapes#unicode-code-point
• https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/fromCharCode
• https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/fromCodePoint