Can someone suggest a way to compare the values of two dates greater than, less than, and not in the past using JavaScript? The values will be coming from text boxes.
In JavaScript, we can compare two dates by converting them into numeric values to correspond to their time. First, we can convert the Date into a numeric value by using the getTime() function. By converting the given dates into numeric values we can directly compare them.
For comparing the two dates, we have used the compareTo() method. If both dates are equal it prints Both dates are equal. If date1 is greater than date2, it prints Date 1 comes after Date 2. If date1 is smaller than date2, it prints Date 1 comes after Date 2.
The Date object will do what you want - construct one for each date, then compare them using the >
, <
, <=
or >=
.
The ==
, !=
, ===
, and !==
operators require you to use date.getTime()
as in
var d1 = new Date(); var d2 = new Date(d1); var same = d1.getTime() === d2.getTime(); var notSame = d1.getTime() !== d2.getTime();
to be clear just checking for equality directly with the date objects won't work
var d1 = new Date(); var d2 = new Date(d1); console.log(d1 == d2); // prints false (wrong!) console.log(d1 === d2); // prints false (wrong!) console.log(d1 != d2); // prints true (wrong!) console.log(d1 !== d2); // prints true (wrong!) console.log(d1.getTime() === d2.getTime()); // prints true (correct)
I suggest you use drop-downs or some similar constrained form of date entry rather than text boxes, though, lest you find yourself in input validation hell.
For the curious, date.getTime()
documentation:
Returns the numeric value of the specified date as the number of milliseconds since January 1, 1970, 00:00:00 UTC. (Negative values are returned for prior times.)
The easiest way to compare dates in javascript is to first convert it to a Date object and then compare these date-objects.
Below you find an object with three functions:
dates.compare(a,b)
Returns a number:
dates.inRange (d,start,end)
Returns a boolean or NaN:
dates.convert
Used by the other functions to convert their input to a date object. The input can be
.
// Source: http://stackoverflow.com/questions/497790 var dates = { convert:function(d) { // Converts the date in d to a date-object. The input can be: // a date object: returned without modification // an array : Interpreted as [year,month,day]. NOTE: month is 0-11. // a number : Interpreted as number of milliseconds // since 1 Jan 1970 (a timestamp) // a string : Any format supported by the javascript engine, like // "YYYY/MM/DD", "MM/DD/YYYY", "Jan 31 2009" etc. // an object : Interpreted as an object with year, month and date // attributes. **NOTE** month is 0-11. return ( d.constructor === Date ? d : d.constructor === Array ? new Date(d[0],d[1],d[2]) : d.constructor === Number ? new Date(d) : d.constructor === String ? new Date(d) : typeof d === "object" ? new Date(d.year,d.month,d.date) : NaN ); }, compare:function(a,b) { // Compare two dates (could be of any type supported by the convert // function above) and returns: // -1 : if a < b // 0 : if a = b // 1 : if a > b // NaN : if a or b is an illegal date // NOTE: The code inside isFinite does an assignment (=). return ( isFinite(a=this.convert(a).valueOf()) && isFinite(b=this.convert(b).valueOf()) ? (a>b)-(a<b) : NaN ); }, inRange:function(d,start,end) { // Checks if date in d is between dates in start and end. // Returns a boolean or NaN: // true : if d is between start and end (inclusive) // false : if d is before start or after end // NaN : if one or more of the dates is illegal. // NOTE: The code inside isFinite does an assignment (=). return ( isFinite(d=this.convert(d).valueOf()) && isFinite(start=this.convert(start).valueOf()) && isFinite(end=this.convert(end).valueOf()) ? start <= d && d <= end : NaN ); } }
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