Math&Date

math物件提供數學相關參數與方法供我們使用，Math內的方法都是static，所以不需要建立，直接使用Math.XXX來呼叫。Date也是內建物件，使用new關鍵字建立，可以讓我們操作時間的顯示，在之後介紹。

Math properties

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而其擁有的屬性如下:>>

1. Math.E: Euler's number -> 2.718
2. Math.LN2: Natural logarithm of 2 -> 0.693
3. Math.LOG2E: Base 2 logarithm of E -> 1.442
4. Math.LOG10E: Base 10 logarithm of E -> 0.434
5. Math.PI: pi -> 3.14159
6. Math.SQRT1_2: Square root of 1/2 -> 0.707
7. Math.SQRT2: Square root of 2 -> 1.414

>>
console.log("E: " + Math.E + "\nLN2: " + Math.LN2 + "\nLN10: " + Math.LN10 + "\nLOG2E: " + Math.LOG2E + "\nLOG10E: " + Math.LOG10E + "\nPI: " + Math.PI+ "\nSQRT1_2: " + Math.SQRT1_2 + "\nSQRT2: " + Math.SQRT2);

Math methods

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Math的相關方法計有如下:

1. Math.abs(x): absolute value
2. Math.acos(x): arccosine (in radians)
3. Math.asin(x): arcsine (in radians)
4. Math.atan(x): arctangent (in radians)
5. Math.atan2(x,y): arctanget of the quotient of its arguments
6. Math.ceil(x): smallest integer greater than of equal to x
7. Math.cos(x): cosine
8. Math.exp(x): e^x
9. Math.floor(x): largest integer less than or equal to x
10. Math.log(x): log_ex(ln(x))
11. Math.max(x,y,...): largest number
12. Math.min(x,y,...): smallest number
13. Math.pow(x,y): x^y
14. Math.random(): random number between 0 and 1
15. Math.round(x): a number rounded to the nearest integer
16. Math.sin(x): sine
17. Math.sqrt(x): square root of x
18. Math.tan(x): tangent

Date

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Date的宣告方式可以有以下幾種:

• new Date()
• new Date(milliseconds): 1/1/70 + milliseconds
• new Date(datestring): "yyyy-mm-dd", "yyyy-mm", "yyyy", "yyyy-mm-ddThh:mm:ssZ"(Z:UTC time), "yyyy", "yyyy-mm-ddThh:mm:ss-hh:mm" (compare to UTC), "mm/dd/yyyy", "mmm dd yyyy" (Jul 10 2000)
• new Date(year, month, date[, hours, minutes, seconds, milliseconds])

Date methods

1. Date(): today's date and time. >> console.log(Date());
2. getDate(): returns day of the month. >> var d = new Date("December 31, 1999, 23:59:59"); console.log(d.getDate());
3. getDay(): returns day of the week. >> console.log(d.getDay());
4. getFullYear(): returns the year. >> console.log(d.getFullYear());
5. getHours(): returns the hour. >> console.log(d.getHours());
6. getMilliseconds(): returns milliseconds. >> console.log(d.getMilliseconds());
7. getMinutes(): returns the minutes. >> console.log(d.getMinutes());
8. getMonth(): returns the month. >> console.log(d.getMonth());
9. getSeconds(): returns the seconds. >> console.log(d.getSeconds());
10. getTime(): returns the numeric value of time (milliseconds since January 1, 1970, 00:00:00 UTC). >> console.log(d.getTime()); console.log(Date.parse(d)); console.log(d.valueOf()); or use Date.parse() method or valueOf() method.
11. getTimezoneOffset(): returns the time-zone offset in minutes. >> console.log(d.getTimezoneOffset());
12. getUTCDate(): returns the date of the month according to universal time. >> console.log(d.getUTCDate());
13. getUTCDay(): returns the day of the week according to universal time. >> console.log(d.getUTCDay());
14. getUTCFullYear(): returns the year according to universal time. >> console.log(d.getUTCFullYear());
15. getUTCHours: returns the hours according to universal time. >> console.log(d.getUTCHours());
16. getUTCMilliseconds(): returns the milliseconds according to universal time. >> console.log(d.getUTCMilliseconds());
17. getUTCMinutes(): returns the minutes according to universal time. >> console.log(d.getUTCMinutes());
18. getUTCMonth(): returns the month according to universal time. >> console.log(d.getUTCMonth());
19. getUTCSeconds(): returns the seconds according to universal time. >> console.log(d.getUTCSeconds());
20. setDate(): sets the day of month. >> d.setDate(1); console.log(d);
21. setFullYear(): sets the year. >> d.setFullYear(2018); console.log(d);
22. setHours(): sets the hour. >> d.setHours(12); console.log(d);
23. setMilliseconds(): sets the Milliseconds. >> d.setMilliseconds(12); console.log(d);
24. setMinutes(): sets the Minutes. >> d.setMilliseconds(12); console.log(d);
25. setMonth(): sets the Month. >> d.setMilliseconds(12); console.log(d);
26. setSeconds(): sets the Seconds. >> d.setMilliseconds(12); console.log(d);
27. setTime(): sets the Date object to the time represented by a milliseconds >> d.setTime(9466559990000); console.log(d);
28. setUTCDate(): sets the day of the month according to universal time. >> d.setUTCDate(10); console.log(d);
29. setUTCFullYear(): sets the year according to universal time. >> d.setUTCFullYear(2250); console.log(d);
30. setUTCHours(): sets the hour according to universal time. >> d.setUTCHours(10); console.log(d);
31. setUTCMilliseconds(): sets the milliseconds according to universal time. >> d.setUTCMilliseconds(86400000); console.log(d);
32. setUTCMinutes(): sets the minutes according to universal time. >> d.setUTCMinutes(30); console.log(d);
33. setUTCMonth(): sets the month according to universal time. >> d.setUTCMonth(6); console.log(d);
34. setUTCSeconds(): sets the seconds according to universal time. >> d.setUTCSeconds(75); console.log(d);
35. toDateString(): returns date. >> console.log(d.toDateString());
36. toLocaleDateString(): returns date using current locale's conventions. >> console.log(d.toLocaleDateString());
37. toLocaleString(): converts a date to a string, using current locale's conventions. >> console.log(d.toLocaleString());
38. toLocaleTimeString(): returns the time of the Date, using current locale's conventions. >> console.log(d.toLocaleTimeString());
39. toString(): returns a String of a Date object. >> console.log(d.toString());
40. toTimeString(): returns a String of time of a Date object. >> console.log(d.toTimeString());
41. toUTCString(): returns a String of time of a Date object according to universal time. >> console.log(d.toUTCString());

Time Comparison

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比較兩時間的先後。 >>
var now = new Date(Date.now()); var oneday = new Date("06/15/2018"); if(now > oneday){ console.log(now.toString() + " is after " + oneday.toString()); }else{ console.log(now.toString() + " is before " + oneday.toString()); }