計算一個人有多少天？

Question

我需要計算出某人有多少天，但我不確定數學。這是我到目前爲止有：

var birthYear = parseInt(prompt ('Enter your birth year:')); 
var birthMonth = prompt ('Enter the name of the month of birth:'); 
var birthDay = parseInt(prompt ('Enter your day of birth as an integer:')); 
var milliDay = 1000*60*60*24; //Milliseconds in a day 
monthAbb = 'janfebmaraprmayjunjulaugsepoctnovdec'; 
chineseZod = 12; 
zodCycle = 1924; //Chinese Zodiac Cycle 
var zodAnimal = new Array('Rat','Ox','Tiger','Rabbit','Dragon','Snake','Horse','Goat','Monkey','Rooster','Dog','Pig'); 
var zodAnimalD = new Array('Forthright, tenacious, intense, meticulous, charismatic, sensitive, intellectual, industrious, charming, eloquent, sociable, artistic, and shrewd. Can be manipulative, vindictive, self-destructive, envious, mendacious, venal, obstinate, critical, over-ambitious, ruthless, intolerant, and scheming.','Dependable, ambitious, calm, methodical, born leader, patient, hardworking, conventional, steady, modest, logical, resolute, and tenacious. Can be stubborn, dogmatic, hot-tempered, narrow-minded, materialistic, rigid, and demanding.','Unpredictable, rebellious, colorful, powerful, passionate, daring, impulsive, vigorous, stimulating, sincere, affectionate, humanitarian, and generous. Can be restless, reckless, impatient, quick-tempered, obstinate, selfish, aggressive, and moody.','Gracious, good friend, kind, sensitive, soft-spoken, amiable, elegant, reserved, cautious, artistic, thorough, tender, self-assured, shy, astute, compassionate, lucky, and flexible. Can be moody, detached, superficial, self-indulgent, opportunistic, and stubborn.','Magnanimous, stately, vigorous, strong, self-assured, proud, noble, direct, dignified, eccentric, intellectual, fiery, passionate, decisive, pioneering, artistic, generous, and loyal. Can be tactless, arrogant, imperious, tyrannical, demanding, intolerant, dogmatic, violent, impetuous, and brash.','Deep thinker, wise, mystic, graceful, soft-spoken, sensual, creative, prudent, shrewd, elegant, cautious, responsible, calm, strong, constant, and purposeful. Can be a loner, bad communicator, possessive, hedonistic, self-doubting, distrustful, mendacious, suffocating, and cold.','Cheerful, popular, quick-witted, changeable, earthy, perceptive, talkative, agile, magnetic, intelligent, astute, flexible, and open-minded. Can be fickle, arrogant, childish, anxious, rude, gullible, and stubborn.','Righteous, sincere, sympathetic, mild-mannered, observant, artistic, intellectual, ingenious, innovative, creative, mothering, peaceful, and generous. Can be indecisive, over-passive, worrier, pessimistic, sensitive, shy, and weak-willed.','Inventor, motivator, improviser, quick-witted, inquisitive, flexible, innovative, problem solver, self-assured, sociable, artistic, polite, dignified, competitive, objective, and factual. Can be egotistical, vain, arrogant, selfish, reckless, snobbish, deceptive, manipulative, cunning, jealous, suspicious, and stubborn.',' Acute, neat, meticulous, organized, self-assured, decisive, conservative, critical, perfectionist, alert, zealous, practical, scientific, and responsible. Can be over zealous and critical, puritanical, egotistical, abrasive, proud, opinionated, and gives into empty bravado.','Honest, intelligent, straightforward, loyal, sense of justice and fair play, attractive, amicable, unpretentious, sociable, open-minded, idealistic, moralistic, practical, affectionate, sensitive, and easy going. Can be cynical, lazy, cold, judgmental, pessimistic, worrier, stubborn, and quarrelsome.','Honest, gallant, sturdy, sociable, peace-loving, patient, loyal, hard-working, trusting, sincere, calm, understanding, thoughtful, scrupulous, passionate, and intelligent. Can be naive, over-reliant, self-indulgent, gullible, fatalistic, and materialistic.'); 
var monthArr = new Array(11); 

monthArr [0] = "jan"; 
monthArr [1] = "feb"; 
monthArr [2] = "mar"; 
monthArr [3] = "apr"; 
monthArr [4] = "may"; 
monthArr [5] = "jun"; 
monthArr [6] = "jul"; 
monthArr [7] = "aug"; 
monthArr [8] = "sep"; 
monthArr [9] = "oct"; 
monthArr [10] = "nov"; 
monthArr [11] = "dec"; 

var monthNum = monthAbb.indexOf(birthMonth.slice(0, 3).toLowerCase())/3; 
alert(monthNum); 
var d = new Date (birthYear, monthNum, birthDay); 
alert(d); 
var dCurrent = new Date(); 
dCurrent = dCurrent.getTime(); //Grabs the time of the current date in milliseconds. 
var dTotal = dCurrent - d; 
alert(dTotal); 
dTotal = dTotal/milliDay; 
dTotal = Math.floor(dTotal); //7193 
alert(dTotal + ' is after division'); 
dTotal = dTotal/365.25; 
dTotal = Math.floor(dTotal); 
alert(dTotal + ' is how old you are!'); 
dTotal = birthYear - zodCycle; 
dTotal = dTotal % chineseZod; 
alert(dTotal); 
alert(d); 
var testS; 
testS = dCurrent - d; 
testS = testS/milliDay; 
testS = testS * 365.25; 
document.write("<span style=\"color: red;\">" + 'Your birthday is ' + d.toDateString() + "</span>"); 
alert(testS); 

Answer 1

我不太確定究竟如何在JavaScript中實現這一點，但你爲什麼不基於用戶的出生日期時間戳，從目前的減去它時間戳，然後（假設時間戳以秒爲單位）將其除以一天中的秒數？

Answer 2

這實際上比這更容易。一旦你有兩個日期（自己的生日和「現在」），你只需做到這一點：

var days = Math.floor((now - birthDate)/86400000); 

這是因爲在JavaScript中，因爲大紀元毫秒Date objects保持時間，當你對他們做數學，他們使用該毫秒值（並且結果是毫秒數）。而且JavaScript每天準確的假設爲86,400,000毫秒。

所以一旦你有birthYear，monthNum，並birthDay：

var birthDate = new Date(birthYear, monthNum, birthDay); 
var days = Math.floor((new Date() - birthdate)/86400000); 

Live example using a datepicker | source