日期比较无法正常工作

Question

Hi I have the following if then statement in my JS code.

    if (attributes.DATE > '10/20/2013'){
        html += '<b>Maximum percentage:</b> ' + aPerc + '%';
    }
    else {
        html += '<b>Percentage:</b> ' + aPerc + '%';    
    }

It seems to be working fine for October 2013 dates, and all January dates (no matter the year).

For past October years, it will display "Maximum percentage:" for Oct. 1-19 and "Percentage" for Oct. 20-31st.

It does not work correctly for other months. Eg Feb, March, April, etc. it displays "Maximum Percentage".

I am guessing it has something to do with my date format? Thank you.

Answer 1

I would do this:

var date1 = new Date(attributes.DATE);
var date2 = new Date('10/20/2013');

if (date1 > date2){
    html += '<b>Maximum percentage:</b> ' + aPerc + '%';
}
else {
    html += '<b>Percentage:</b> ' + aPerc + '%';    
}

That way, you're comparing two date objects rather than two string objects.

Answer 2

You're doing a string comparison, but the order of the fields in the string will not give you a date-order comparison. (You'd get one if both strings were in yyyy/MM/dd order...)

If DATE is a Date instance, you can do this:

if (attributes.DATE >= new Date(2013, 9, 21)){

...which will be true from midnight on October 21st (the month value starts with 0 = January, so 9 = October). Note I made it >= and the 21st rather than the 20th, because I assumed if you're looking for something > '10/20/2013' , you mean the 21st or later (as opposed to meaning "any time after midnight on the 20th").