现在好多的ID都是服务器端生成的，当然JS也可以生成GUID或者UUID之类的，但是如果想要有序……这时就想到了雪花算法，但是都知道JS中Number的最大值为Number.MAX_SAFE_INTEGER：9007199254740991。在雪花算法中，有的操作在JS中会溢出。不过还好，网上有好多BigInt的类库，例如本例使用的：http://peterolson.github.io/BigInteger.js/ ，还有就是chrome67 原生支持BigInt类型，这是个好消息……
参考文章： 理解分布式id生成算法SnowFlake
类库：http://peterolson.github.io/BigInteger.js/
记录一下代码
类库方式实现：
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta http-equiv="X-UA-Compatible" content="ie=edge"> <title>Document</title> </head> <body> <script src="https://cdnjs.cloudflare.com/ajax/libs/big-integer/1.6.32/BigInteger.min.js"></script> <!-- <script src="http://peterolson.github.com/BigInteger.js/BigInteger.min.js"></script> --> <script> var Snowflake = /** @class */ (function() { function Snowflake(_workerId, _dataCenterId, _sequence) { // this.twepoch = 1288834974657; this.twepoch = 0; this.workerIdBits = 5; this.dataCenterIdBits = 5; this.maxWrokerId = -1 ^ (-1 << this.workerIdBits); // 值为：31 this.maxDataCenterId = -1 ^ (-1 << this.dataCenterIdBits); // 值为：31 this.sequenceBits = 12; this.workerIdShift = this.sequenceBits; // 值为：12 this.dataCenterIdShift = this.sequenceBits + this.workerIdBits; // 值为：17 this.timestampLeftShift = this.sequenceBits + this.workerIdBits + this.dataCenterIdBits; // 值为：22 this.sequenceMask = -1 ^ (-1 << this.sequenceBits); // 值为：4095 this.lastTimestamp = -1; //设置默认值,从环境变量取 this.workerId = 1; this.dataCenterId = 1; this.sequence = 0; if (this.workerId > this.maxWrokerId || this.workerId < 0) { throw new Error('config.worker_id must max than 0 and small than maxWrokerId-[' + this.maxWrokerId + ']'); } if (this.dataCenterId > this.maxDataCenterId || this.dataCenterId < 0) { throw new Error('config.data_center_id must max than 0 and small than maxDataCenterId-[' + this.maxDataCenterId + ']'); } this.workerId = _workerId; this.dataCenterId = _dataCenterId; this.sequence = _sequence; } Snowflake.prototype.tilNextMillis = function(lastTimestamp) { var timestamp = this.timeGen(); while (timestamp <= lastTimestamp) { timestamp = this.timeGen(); } return timestamp; }; Snowflake.prototype.timeGen = function() { //new Date().getTime() === Date.now() return Date.now(); }; Snowflake.prototype.nextId = function() { var timestamp = this.timeGen(); if (timestamp < this.lastTimestamp) { throw new Error('Clock moved backwards. Refusing to generate id for ' + (this.lastTimestamp - timestamp)); } if (this.lastTimestamp === timestamp) { this.sequence = (this.sequence + 1) & this.sequenceMask; if (this.sequence === 0) { timestamp = this.tilNextMillis(this.lastTimestamp); } } else { this.sequence = 0; } this.lastTimestamp = timestamp; var shiftNum = (this.dataCenterId << this.dataCenterIdShift) | (this.workerId << this.workerIdShift) | this.sequence; // dataCenterId:1,workerId:1,sequence:0 shiftNum:135168 var nfirst = new bigInt(String(timestamp - this.twepoch), 10); nfirst = nfirst.shiftLeft(this.timestampLeftShift); var nnextId = nfirst.or(new bigInt(String(shiftNum), 10)).toString(10); return nnextId; }; return Snowflake; }()); var tempSnowflake = new Snowflake(1, 1, 0); var tempIds = []; console.time(); for (var i = 0; i < 10000; i++) { var tempId = tempSnowflake.nextId(); console.log(tempId); if (tempIds.indexOf(tempId) < 0) { tempIds.push(tempId); } } console.log(tempIds.length); console.timeEnd(); </script> </body> </html>
原生BigInt实现：
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta http-equiv="X-UA-Compatible" content="ie=edge"> <title>Document</title> </head> <body> <script> var Snowflake = /** @class */ (function() { function Snowflake(_workerId, _dataCenterId, _sequence) { this.twepoch = 1288834974657n; //this.twepoch = 0n; this.workerIdBits = 5n; this.dataCenterIdBits = 5n; this.maxWrokerId = -1n ^ (-1n << this.workerIdBits); // 值为：31 this.maxDataCenterId = -1n ^ (-1n << this.dataCenterIdBits); // 值为：31 this.sequenceBits = 12n; this.workerIdShift = this.sequenceBits; // 值为：12 this.dataCenterIdShift = this.sequenceBits + this.workerIdBits; // 值为：17 this.timestampLeftShift = this.sequenceBits + this.workerIdBits + this.dataCenterIdBits; // 值为：22 this.sequenceMask = -1n ^ (-1n << this.sequenceBits); // 值为：4095 this.lastTimestamp = -1n; //设置默认值,从环境变量取 this.workerId = 1n; this.dataCenterId = 1n; this.sequence = 0n; if (this.workerId > this.maxWrokerId || this.workerId < 0) { throw new Error('_workerId must max than 0 and small than maxWrokerId-[' + this.maxWrokerId + ']'); } if (this.dataCenterId > this.maxDataCenterId || this.dataCenterId < 0) { throw new Error('_dataCenterId must max than 0 and small than maxDataCenterId-[' + this.maxDataCenterId + ']'); } this.workerId = BigInt(_workerId); this.dataCenterId = BigInt(_dataCenterId); this.sequence = BigInt(_sequence); } Snowflake.prototype.tilNextMillis = function(lastTimestamp) { var timestamp = this.timeGen(); while (timestamp <= lastTimestamp) { timestamp = this.timeGen(); } return BigInt(timestamp); }; Snowflake.prototype.timeGen = function() { return BigInt(Date.now()); }; Snowflake.prototype.nextId = function() { var timestamp = this.timeGen(); if (timestamp < this.lastTimestamp) { throw new Error('Clock moved backwards. Refusing to generate id for ' + (this.lastTimestamp - timestamp)); } if (this.lastTimestamp === timestamp) { this.sequence = (this.sequence + 1n) & this.sequenceMask; if (this.sequence === 0n) { timestamp = this.tilNextMillis(this.lastTimestamp); } } else { this.sequence = 0n; } this.lastTimestamp = timestamp; return ((timestamp - this.twepoch) << this.timestampLeftShift) | (this.dataCenterId << this.dataCenterIdShift) | (this.workerId << this.workerIdShift) | this.sequence; }; return Snowflake; }()); console.time(); var tempSnowflake = new Snowflake(1n, 1n, 0n); var tempIds = []; for (var i = 0; i < 10000; i++) { var tempId = tempSnowflake.nextId(); console.log(tempId); if (tempIds.indexOf(tempId) < 0) { tempIds.push(tempId); } } console.log(tempIds.length); console.timeEnd(); </script> </body> </html>
好像原生效果更好一些，到此结束。