Javascript is the best way to compare dates
I would like to collect all opinions on what is the correct way to sort dates in Javascript.
Check out the code snippets below, I have 2 scripts to sort dates using:
i) javascript date object
ii) custom javascript date string format
May I know why, when I sort by custom javascript date format, the display of the final results seems to be wrong compared to sorting using javascript date objects.
Should I sort the date using javascript date objects?
Date.prototype.getDateFormat = function (value) {
var d = this.getDate();
if (d < 10)
d = "0" + d;
var month = this.getMonth() + 1;
if (month < 10)
month = "0" + month;
return value.replace("MM", month).replace("dd", d).replace("yyyy", this.getFullYear());
}
Date.prototype.getTimeFormat = function (value) {
var h = this.getHours();
var m = this.getMinutes();
var s = this.getSeconds();
var a = "AM";
if (h == 12) {
a = "PM";
} else if (h > 12) {
a = "PM";
h = h - 12;
}
if (h < 10) {
h = "0" + h;
}
if (m < 10) {
m = "0" + m;
}
if (s < 10) {
s = "0" + s;
}
return value.replace("hh", h).replace("mm", m).replace("ss", s).replace("tt", a);
}
function sortDateTime(a,b){
if(a > b) return 1;
else if(a < a) return -1;
}
var dateList1 = [];
var dateList2 = [];
// Using pure Javascript Date Object
var date1 = new Date("06/03/2017 12:00:00 PM");
var date2 = new Date("06/03/2017 03:00:00 PM");
var date3 = new Date("06/03/2017 05:00:00 PM");
dateList1.push(date1);
dateList1.push(date2);
dateList1.push(date3);
var result1 = dateList1.sort(sortDateTime);
for(var e = 0 ; e < result1.length ; e++){
var display = "<div>" + result1[e] + "</div>";
$("#result1").append(display);
}
//Result from result1 List
// 1) 06/03/2017 12:00:00 PM
// 2) 06/03/2017 03:00:00 PM
// 3) 06/03/2017 05:00:00 PM
// Using Javascript Date Time custom string format
var pDate1 = new Date("06/03/2017 12:00:00 PM");
var pDate2 = new Date("06/03/2017 03:00:00 PM");
var pDate3 = new Date("06/03/2017 05:00:00 PM");
var rDate1 = pDate1.getDateFormat("yyyyMMdd") + pDate1.getTimeFormat(" tt hhmmss");
var rDate2 = pDate2.getDateFormat("yyyyMMdd") + pDate2.getTimeFormat(" tt hhmmss");
var rDate3 = pDate3.getDateFormat("yyyyMMdd") + pDate3.getTimeFormat(" tt hhmmss");
dateList2.push(rDate1);
dateList2.push(rDate2);
dateList2.push(rDate3);
var result2 = dateList2.sort(sortDateTime);
for(var e = 0 ; e < result2.length ; e++){
var display = "<div>" + result2[e] + "</div>";
$("#result2").append(display);
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<b> Sort by Javascript Date object</b>
<div id="result1"></div>
<br/>
<b> Sort by Javascript Custom Date Time string Format</b>
<div id="result2"></div>
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1 answer
Your problem is sortDateTime function. It skips the condition when a == b
and it compares strings and dates as if they were of the same type. Consider:
function sortDateTime(a, b) {
// If strings, compare as strings
if (typeof a == 'string') {
return a.localeCompare(b);
}
// Otherwise, compare as numbers
return a - b;
}
var data = ['2017-03-06T12:00:00','2017-03-06T03:00:00','2017-03-06T17:00:00'];
// Copy and sort as strings
// The strings should be parsed as local, but Safari will parse them as UTC
// They'll be sorted in the same order, they'll just be offset by the host offset
var x = data.slice();
console.log(x.sort(sortDateTime));
// Copy and convert to Dates, then sort
var y = data.map(function(s){return new Date(s)});
console.log(y.sort(sortDateTime));
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