如何构建一个关注出现次数而不是出现位置的正则表达式？

if re.match(r"""
        # Match string having max one each of A,B,C or D.
        ^                      # Anchor to start of string.
        (?=[^A]*(?:A[^A]*)?$)  # Assert zero or one A max.
        (?=[^B]*(?:B[^B]*)?$)  # Assert zero or one B max.
        (?=[^C]*(?:C[^C]*)?$)  # Assert zero or one C max.
        (?=[^D]*(?:D[^D]*)?$)  # Assert zero or one D max.
        [ABCD]+                # One or more of [ABDC].
        Z                     # Anchor to end of string.
        """,text,re.VERBOSE):
    # Successful match at the start of the string
else:
    # Match attempt failed

这是一个JavaScript版本：

var re = /^(?=[^A]*(?:A[^A]*)?$)(?=[^B]*(?:B[^B]*)?$)(?=[^C]*(?:C[^C]*)?$)(?=[^D]*(?:D[^D]*)?$)[ABCD]+$/;
if (re.test(text)) {
    // Successful match
} else {
    // Match attempt failed
}