functional-blockchain
The implementation is refering to this blog.
Blockchain consist of blocks that are chained together. A representation of block could look like this:
{
timestamp: 1568468720410,
data: "I am a block", // could be anything – number, object, etc.
previousHash: "2510c39011c5be704182423e3a695e91", // hash that reference to previous block, thus it is chained
hash: "363b122c528f54df4a0446b6bab05515" // hash of the data of the current block, if the data changes, hash changes
}Since every block represent the previous blocks, then if the previous block changes, the rest of the blocks that chained afterwards will become invalid.