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<script type="text/javascript"> | |
// First let's create an array of JavaScript Date | |
// objects. | |
// More info about the Date class: | |
// http://w3schools.com/js/js_obj_date.asp | |
var dates = [ | |
new Date(2010, 4, 10, 10, 07, 16), | |
new Date(2010, 4, 8, 9, 16, 09), | |
new Date(2010, 3, 30, 0, 15, 49), | |
new Date(2010, 3, 8, 10, 08, 35)]; | |
// Now we will define our date comparison functions. These are callbacks | |
// that we will be providing to the array sort method below. | |
var date_sort_asc = function (date1, date2) { | |
// This is a comparison function that will result in dates being sorted in | |
// ASCENDING order. As you can see, JavaScript's native comparison operators | |
// can be used to compare dates. This was news to me. | |
if (date1 > date2) return 1; | |
if (date1 < date2) return -1; | |
return 0; | |
}; | |
var date_sort_desc = function (date1, date2) { | |
// This is a comparison function that will result in dates being sorted in | |
// DESCENDING order. | |
if (date1 > date2) return -1; | |
if (date1 < date2) return 1; | |
return 0; | |
}; | |
// Finally, we are now able to call the sort method on our array of dates. | |
// More info about array sorting: http://w3schools.com/jsref/jsref_sort.asp | |
// First let's sort the array in ascending order. | |
dates.sort(date_sort_asc); | |
// Now let's output the results to the page to show that the dates are now | |
// sorted in ascending order. | |
document.write('<p>Dates sorted in ascending order (oldest to newest):</p>'); | |
for (var i = 0; i < dates.length; i++) { | |
document.write(i + ': ' + dates[i] + '<br>'); | |
} | |
// Now let's sort the dates in descending order and output the results. | |
dates.sort(date_sort_desc); | |
document.write('<p>Dates sorted in descending order (newest to oldest):</p>'); | |
for (var i = 0; i < dates.length; i++) { | |
document.write(i + ': ' + dates[i] + '<br>'); | |
} | |
// That's all there is to it! | |
// From: http://onpub.com/index.php?s=7&a=109 | |
</script> |
is there any technique to generate dates from one date to another date using looping construct?
@saich Array.prototype.sort()
will not work as you're hoping. The MDN docs state that if you omit a custom sort function:
The array is sorted according to each character's Unicode code point value, according to the string conversion of each element.
This means that each date will be toString-ed to a date string such as Sun Aug 21 2016 00:00:00 GMT-0600 (MDT)
first, then each character, starting from the left, will have it's Unicode point value compared one at a time. This results in unexpected behavior in the sort, since it will essentially sort the array by days of the week first instead of absolute time of each date.
The <
and >
operators call the Object.prototype.valueOf()
function for each operand, then compare the values. This means that a <
or >
comparison between two dates calls the Date.prototype.valueOf()
function for each date object before comparing the values, giving an accurate, absolute comparison.
probably late but also a simple subtraction of data prototypes to sort function would work just fine , reduce unnecessary return -1
like :
var date_sort_asc = function (date1, date2) {
// Accending order.
return date2 - date1
};
even better es6 one-liner:
dataArray.sort((a,b)=> b-a)
Thanks!
@obonyojimmy that is not working in my environment. Node.js version 9.
Won't work because it returns NaN , compare and return yourself @lancedolan
I think @obonyojimmy 's functions actually sort in descending order. Switch to dateArray.sort((a,b)=> a-b)
for ascending.
For anyone who comes across this looking from a TS compliant approach.
dataArray.sort((a,b)=> Number(a)-Number(b))
dates.sort() would work just fine for ascending order... Reversing it would give descending order...