bcrypt no need to store salt?

Question

I'm confused with bcrypt, I would think I would need to store my salt, and then compare my plain text password + salt to the hashed password, however from documentation it does not look like storing the salt is necessary at all. Indeed I used this code to create salt and hashed password:

  let salt = await bcrypt.genSalt(10);

  const saltpasshash = await new Promise((resolve, reject) => {
    bcrypt.hash(plain_text_password, salt, function(err, hash) {
      if (err) reject(err)
      resolve(hash)
    });
  })

  //NOTE I SAVE saltpasshash as users pass and the salt in a separate field in the users table.

This works, what I am confused about is it will then return a valid result if I compare as follows:

valid = await bcrypt.compare(plain_text_password, user.saltpasshash);

I'm confused as to why this would be valid when I am not providing the salt, and if so, why store the salt at all?

Answer 1

From a description of bcrypt at Wikipedia:

... The rest of the hash string includes the cost parameter, a 128-bit salt (Radix-64 encoded as 22 characters), and 184 bits of the resulting hash value (Radix-64 encoded as 31 characters)

Thus, the salt is automatically included in the output string which means there is no need to add it by yourself.