How do I apply a skin tone to an emoji in JavaScript?

Question

Given this emoji, how can I programmatically apply a skin tone in JavaScript?

Grinning face is 0x1F600.

Dark Skin Tone is 0x1F3FF.

Do I simply concatenate the values together?

The following code, based on the algorithm here, merely prints two characters out.

function units(codepoint) {
    const tmp = codepoint - 0x10000
    const padded = tmp.toString(2).padStart(20, '0')
    const unit1 = Number.parseInt(padded.substr(0, 10), 2) + 0xD800;
    const unit2 = Number.parseInt(padded.substr(10), 2) + 0xDC00;
    return [unit1, unit2]
}

const face = units(0x1F600)
const tone = units(0x1F3FF)
const ch = String.fromCharCode(...face, ...tone) 
console.log(ch) // 😀🏿

Answer 1

There are only few emojis that actually take up Skin Tones. For example, faces - man and women facepalming:

function units(codepoint) {
    const tmp = codepoint - 0x10000
    const padded = tmp.toString(2).padStart(20, '0')
    const unit1 = Number.parseInt(padded.substr(0, 10), 2) + 0xD800;
    const unit2 = Number.parseInt(padded.substr(10), 2) + 0xDC00;
    return [unit1, unit2]
}

const face = units(0x1F926)
const tone = units(0x1F3FF)
const ch = String.fromCharCode(...face, ...tone) 
console.log(ch)

It's not possible with others that do not support colour variants. Here, in Every Emoji by Codepoint, you can find those support the Emoji Modifier Fitzpatrick.

No Modifier Support

Modifier Supported