Beacon Chain: Calculate HEAD Slot

ethereum.lib.js

const GENESIS_TIME = "2020-12-01T12:00:23Z"
const MILLISECONDS_PER_SLOT = 12000

function toUTCTimestamp(time) {
    return Date.UTC(
        time.getUTCFullYear(),
        time.getUTCMonth(),
        time.getUTCDate(),
        time.getUTCHours(),
        time.getUTCMinutes(),
        time.getUTCSeconds(),
        time.getUTCMilliseconds()
    )
}

function currentSlot() {
    const genesisTimestamp = toUTCTimestamp(new Date(GENESIS_TIME))
    const currentTime = toUTCTimestamp(new Date)
    return Math.floor((currentTime - genesisTimestamp) / MILLISECONDS_PER_SLOT)
}

console.log(currentSlot())