给出完整代码。怎么在下列代码中使用 Javascript 内置函数记录每次挖矿所消耗的时间。最后对同一难度下的16次挖矿所消耗的时间进行统计计算其平均值。var difficulty = 4; number of zeros required at front of hashvar maximumNonce = 50000000; limit the nonce to this

var difficulty = 4; // number of zeros required at front of hash var maximumNonce = 50000000; // limit the nonce to this so we don't mine too long

// NOTE: Because there are 16 possible characters in a hex value, each time you increment // the difficulty by one you make the puzzle 16 times harder. In my testing, a difficulty // of 6 requires a maximumNonce well over 500,000,000.

///////////////////////// // global variable setup ///////////////////////// var pattern = ''; for (var x = 0; x < difficulty; x++) { pattern += '0'; }

///////////////////////// // functions ///////////////////////// function sha256(block, chain) { // calculate a SHA256 hash of the contents of the block return CryptoJS.SHA256(getText(block, chain)); }

function updateState(block, chain) { // set the well background red or green for this block if ($('#block' + block + 'chain' + chain + 'hash').val().substr(0, difficulty) === pattern) { $('#block' + block + 'chain' + chain + 'well').removeClass('well-error').addClass('well-success'); } else { $('#block' + block + 'chain' + chain + 'well').removeClass('well-success').addClass('well-error'); } }

function updateHash(block, chain) { // update the SHA256 hash value for this block $('#block' + block + 'chain' + chain + 'hash').val(sha256(block, chain)); updateState(block, chain); }

function updateChain(block, chain) { // update all blocks walking the chain from this block to the end for (var x = block; x <= 5; x++) { if (x > 1) { $('#block' + x + 'chain' + chain + 'previous').val($('#block' + (x - 1).toString() + 'chain' + chain + 'hash').val()); } updateHash(x, chain); } }

function mine(block, chain, isChain) { for (var x = 0; x <= maximumNonce; x++) { $('#block' + block + 'chain' + chain + 'nonce').val(x); $('#block' + block + 'chain' + chain + 'hash').val(sha256(block, chain)); if ($('#block' + block + 'chain' + chain + 'hash').val().substr(0, difficulty) === pattern) { if (isChain) { updateChain(block, chain); } else { updateState(block, chain); } break; } } }

var times = []; for (let i = 0; i <16; i++) { const startTime = performance.now(); mine(1,i,true); const finishTime = performance.now(); const time = finishTime - startTime; times.push(time); }

const averageTime = times.reduce((a,b) => a + b, 0) / times.length; console.log("Average time for 16 mines with difficulty " + difficulty + ": " + averageTime + " milliseconds.")