Blockchain database download

1. const SHA256 = require(crypto-js/SHA256);< br />class Block{
constructor(index,timestamp,data,previousHash='&# 39;)< br />{
this.index=index;< br />this.timestamp=timestamp;< br />this.data=data;< br />this.previousHash=previousHash;< br />$this.hash=this.calculateHash();< br />}

calculateHash(){
return SHA256(this,index+this.previousHash+this.timestamp+JSON.stringify(this.data)).tostring();< br />}
}
class blockchain{
constructor(){
this.chain=[this.createGenesisBlock()];<
}
/ / create a generated information block
creategenesis block() {
return new block (0, & quot; 01/01/2019",& quot; Genesis block", 0);
/ / the date is the user's data. In fact, it is the hash value obtained by adding several values together. Here, the information is encrypted and the picture is encrypted. Then the data is still stored in the database, but all the data are hash values. To get this data, you must know the hash value of the previous data block. Then, if the hacker needs to crack all the nodes, the hash value is decrypted, Then all the blocks from the first node to the last node can be decrypted to get the real data. So the security of data stored in the blockchain depends on whether the data is encrypted. If the plaintext is not encrypted, then it is not a blockchain
}
/ / get the last block
getlatesblock() {
return this.chain [this.chain. Length-1]
}
/ / create block
addblock (newblock) {
newblock. Previoushash = this. Getlatesblock(). Hash< br />newBlock.hash=newBlock.calculateHash();< br />this.chain.push(newBlock);< br />}
}

2. Chongqing jinwowo: as for how to build a rigorous database, the method of blockchain is to innovate the structure of the database, divide the data into different blocks, link each block to the back of the previous block through specific information, and present a complete set of data in sequence, which is also the source of the three words "blockchain".

3. That's ten times the survival rate he set. If you lose one, you'll get ten. It's set in the game

4. No

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therefore, investors need to choose a reliable bitcoin trading platform. The reference factors are: 1. The longer the running time, the better; 2. The bigger the instry reputation, the better; 3. The larger the team size, the better; 4. Being able to visit<

it is suggested that China choose "fire coin net", which is cooperated by Wukou School of finance of Tsinghua University. Sequoia Capital has invested 10 million US dollars; The choice of coinbase in foreign countries is an important choice for Silicon Valley banks to invest.

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