conditional - (Javascript) multiple condition set for ternary operator issue -

for (var days = 1; days <= 31; ++days) {     console.log(         (days == (1, 31, 21) ? days + 'st':'') ||         (days == (2, 22) ? days + 'nd':'') ||         (days == (3, 23) ? days + 'rd':'') ||         days + 'th'     ); } 

trying display (1st, 2nd, 3rd) (21st, 22nd, 23rd) (31st) (multiple th) i'm getting strange result here, i'm not quite sure i've done wrong, appreciated.

i did try google , figure out, promise, appreciate relatively detailed explanation why behaving strange.

you've typed in code syntactically correct, doesn't mean apparently expect mean.

this:

(days == (1, 31, 21) ? days + 'st':'') 

is in effect same as

(days == 21 ? days + 'st':'') 

the (1, 31, 21) subexpression involves comma operator, allows sequence of expressions (possibly side-effects) evaluated. overall value value of last expression.

if want compare value list of possibilities, in general can

• use sequence of == (or ===) comparisons connected ||;
• use switch statement groups of case clauses;
• use .indexof() value in array.

in particular case, i'd make array containing suffixes , index it:

var suffixes = array.apply(null, new array(32)).map(function() { return "th"; }); suffixes[2] = suffixes[22] = "nd"; suffixes[1] = suffixes[21] = suffixes[31] = "st"; suffixes[3] = suffixes[23] = "rd"; 

then can index array day number suffix.