--description--

Given a donor blood type and a recipient blood type, determine whether the donor can give blood to the recipient.

Each blood type consists of:

• A letter: "A", "B", "AB", or "O"
• And an Rh factor: "+" or "-"

Blood types will be one of the valid letters followed by an Rh factor. For example, "AB+" and "O-" are valid blood types.

Letter Rules:

• "O" can donate to other letter type.
• "A" can donate to "A" and "AB".
• "B" can donate to "B" and "AB".
• "AB" can donate only to "AB".

Rh Rules:

• Negative ("-") can donate to both "-" and "+".
• Positive ("+") can donate only to "+".

Both letter and Rh rule must pass for a donor to be able to donate to the recipient.

--hints--

canDonate("B+", "B+") should return true.

assert.isTrue(canDonate("B+", "B+"));

canDonate("O-", "AB-") should return true.

assert.isTrue(canDonate("O-", "AB-"));

canDonate("O+", "A-") should return false.

assert.isFalse(canDonate("O+", "A-"));

canDonate("A+", "AB+") should return true.

assert.isTrue(canDonate("A+", "AB+"));

canDonate("A-", "B-") should return false.

assert.isFalse(canDonate("A-", "B-"));

canDonate("B-", "AB+") should return true.

assert.isTrue(canDonate("B-", "AB+"));

canDonate("B-", "A+") should return false.

assert.isFalse(canDonate("B-", "A+"));

canDonate("O-", "O+") should return true.

assert.isTrue(canDonate("O-", "O+"));

canDonate("O+", "O-") should return false.

assert.isFalse(canDonate("O+", "O-"));

canDonate("AB+", "AB-") should return false.

assert.isFalse(canDonate("AB+", "AB-"));

--seed--

--seed-contents--

function canDonate(donor, recipient) {

  return donor;
}

--solutions--

function canDonate(donor, recipient) {
  const donorType = donor.slice(0, -1);
  const donorRh = donor.slice(-1);

  const recipientType = recipient.slice(0, -1);
  const recipientRh = recipient.slice(-1);

  const aboCompatibility = {
    "O": ["A", "B", "AB", "O"],
    "A": ["A", "AB"],
    "B": ["B", "AB"],
    "AB": ["AB"]
  };

  const aboMatch = aboCompatibility[donorType].includes(recipientType);
  const rhMatch =
    donorRh === "-" || (donorRh === "+" && recipientRh === "+");

  return aboMatch && rhMatch;
}