the hash of the object (string(32))
hash() // => 'd41d8cd98f00b204e9800998ecf8427e'
hash(1) // => '0ebf66ef421c088eaba5e3b47176d2b3'
hash('1') // the data type is aware => '8e71db5ef074ed1210bee7b7c854365d'
hash({a:1}) // => '0ebf66ef421c088eaba5e3b47176d2b3'
hash({a:1,b:2}) // => '6f2e650dd73e36d596fa487d8cf93f47'
hash({b:2,a:1}) // => '6f2e650dd73e36d596fa487d8cf93f47'
generate hash value from values