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/
CDN：https://cdnjs.com/
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>Documenttitle>
head>
<body>
<script src="https://cdnjs.cloudflare.com/ajax/libs/big-integer/1.6.32/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>Documenttitle>
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。