SalesforceIDを15桁から18桁に変換するコード

function convertSalesforceIdFrom15to18(input) {
  let addon = "";
	for (let block = 0; block < 3; block++) {
		let loop = 0;
		for (let position = 0; position < 5; position++){
			var current=input.charAt(block * 5 + position);
			if(current >= "A" && current <= "Z")
				loop += 1 << position;
		}
		addon += "ABCDEFGHIJKLMNOPQRSTUVWXYZ012345".charAt(loop);
	}
  return `${input}${addon}`;
}

function convertSalesforceIdFrom15to18(string $input): string
{
    $addon = "";
    for ($block = 0; $block < 3; $block++) {
        $loop = 0;
        for ($position = 0; $position < 5; $position++) {
            $index = $block * 5 + $position;
            $current = $input[$index];
            if ($current >= "A" && $current <= "Z") {
                $loop += (1 << $position);
            }
        }
        $checksum_chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ012345";
        $addon .= $checksum_chars[$loop];
    }
    return $input . $addon;
}

const checksumChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ012345"

func convertSalesforceIdFrom15to18(input string) string {
	var addon string
	for block := 0; block < 3; block++ {
		loop := 0
		for position := 0; position < 5; position++ {
			charIndex := block*5 + position
			current := input[charIndex]
			if current >= 'A' && current <= 'Z' {
				loop += 1 << position
			}
		}
		if loop < len(checksumChars) {
			addon += string(checksumChars[loop])
		}
	}
	return input + addon
}