在此页

• 句法
• Polyfill
• 范例
• 规范
• 浏览器兼容性
• 另请参阅
• 相关话题

静态 Date.now() method returns the number of milliseconds elapsed since January 1, 1970 00:00:00 UTC.

句法

var timeInMs = Date.now();
					

返回值

A Number representing the milliseconds elapsed since the UNIX epoch.

Polyfill

This method was standardized in ECMA-262 5 ^th edition. Engines which have not been updated to support this method can work around the absence of this method using the following shim:

if (!Date.now) {
  Date.now = function now() {
    return new Date().getTime();
  };
}
					

范例

Reduced time precision

To offer protection against timing attacks and fingerprinting, the precision of Date.now() might get rounded depending on browser settings.
In Firefox, the privacy.reduceTimerPrecision preference is enabled by default and defaults to 20µs in Firefox 59; in 60 it will be 2ms.

// reduced time precision (2ms) in Firefox 60
Date.now()
// 1519211809934
// 1519211810362
// 1519211811670
// ...
// reduced time precision with `privacy.resistFingerprinting` enabled
Date.now();
// 1519129853500
// 1519129858900
// 1519129864400
// ...
					

In Firefox, you can also enable privacy.resistFingerprinting , the precision will be 100ms or the value of privacy.resistFingerprinting.reduceTimerPrecision.microseconds , whichever is larger.

规范

规范
ECMAScript (ECMA-262) The definition of 'Date.now' in that specification.

浏览器兼容性

The compatibility table in this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.

更新 GitHub 上的兼容性数据

	Desktop						Mobile						Server
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet	Node.js
now	Chrome 5	Edge 12	Firefox 3	IE 9	Opera 10.5	Safari 4	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 14	Safari iOS 4	Samsung Internet Android 1.0	nodejs 0.1.100

图例

完整支持

完整支持

另请参阅

• Performance.now() — provides timestamps with sub-millisecond resolution for use in measuring web page performance
• console.time / console.timeEnd

元数据

• 最后修改： May 20, 2020

相关话题

1. 标准内置对象
2. Date
3. 方法
   1. Date.UTC()
   2. Date.now()
   3. Date.parse()
   4. Date.prototype.getDate()
   5. Date.prototype.getDay()
   6. Date.prototype.getFullYear()
   7. Date.prototype.getHours()
   8. Date.prototype.getMilliseconds()
   9. Date.prototype.getMinutes()
   10. Date.prototype.getMonth()
   11. Date.prototype.getSeconds()
   12. Date.prototype.getTime()
   13. Date.prototype.getTimezoneOffset()
   14. Date.prototype.getUTCDate()
   15. Date.prototype.getUTCDay()
   16. Date.prototype.getUTCFullYear()
   17. Date.prototype.getUTCHours()
   18. Date.prototype.getUTCMilliseconds()
   19. Date.prototype.getUTCMinutes()
   20. Date.prototype.getUTCMonth()
   21. Date.prototype.getUTCSeconds()
   22. Date.prototype.getYear()
   23. Date.prototype.setDate()
   24. Date.prototype.setFullYear()
   25. Date.prototype.setHours()
   26. Date.prototype.setMilliseconds()
   27. Date.prototype.setMinutes()
   28. Date.prototype.setMonth()
   29. Date.prototype.setSeconds()
   30. Date.prototype.setTime()
   31. Date.prototype.setUTCDate()
   32. Date.prototype.setUTCFullYear()
   33. Date.prototype.setUTCHours()
   34. Date.prototype.setUTCMilliseconds()
   35. Date.prototype.setUTCMinutes()
   36. Date.prototype.setUTCMonth()
   37. Date.prototype.setUTCSeconds()
   38. Date.prototype.setYear()
   39. Date.prototype.toDateString()
   40. Date.prototype.toGMTString()
   41. Date.prototype.toISOString()
   42. Date.prototype.toJSON()
   43. Date.prototype.toLocaleDateString()
   44. Date.prototype.toLocaleString()
   45. Date.prototype.toLocaleTimeString()
   46. Date.prototype.toSource()
   47. Date.prototype.toString()
   48. Date.prototype.toTimeString()
   49. Date.prototype.toUTCString()
   50. Date.prototype.valueOf()
   51. Date.prototype[@@toPrimitive]
4. 继承：
5. Function
6. 特性
   1. Function.arguments
   2. Function.caller
   3. Function.displayName
   4. Function.length
   5. Function.name
7. 方法
   1. Function.prototype.apply()
   2. Function.prototype.bind()
   3. Function.prototype.call()
   4. Function.prototype.toSource()
   5. Function.prototype.toString()
8. Object
9. 特性
   1. Object.prototype.__proto__
   2. Object.prototype.constructor
10. 方法
    1. Object.prototype.__defineGetter__()
    2. Object.prototype.__defineSetter__()
    3. Object.prototype.__lookupGetter__()
    4. Object.prototype.__lookupSetter__()
    5. Object.prototype.hasOwnProperty()
    6. Object.prototype.isPrototypeOf()
    7. Object.prototype.propertyIsEnumerable()
    8. Object.prototype.toLocaleString()
    9. Object.prototype.toSource()
    10. Object.prototype.toString()
    11. Object.prototype.valueOf()
    12. Object.setPrototypeOf()