JavaScript sum the number in the array

Question

I have a following array var total = [10, 0.25, 12.75, 1, 0];

When I do:

 for (var i= 0; i< total.length; i++) {
 totalNo += parseInt(+(total[i]));
 }

The totalNo is always a full number. Looks like the .XX after dot value is skipped. How to make sure it is added properly?

Answer 1

You shouldn't need to run any numeric coercion function (e.g. parseInt) - your array values are already numbers.

If an ECMA5 solution is acceptable, you can use reduce():

var arr = [10, 0.25, 12.75, 1, 0];
alert(arr.reduce(function(curr_total, val) {
 return curr_total + val;
}, 0)); //24

• MaxArt: A callback solution is way slower and could affect performances for large arrays.
• Mitya: @MaxArt - you're seriously voting me down for posting a native solution that does what he needs? You're sure that's a good candidate for vote-down?
• Fabrizio Calderan: you have my +1: in this specific question, the array contain only floating point values so there's no even need to use parseFloat. You correctly noted this
• jAndy: @MaxArt: bull****. jsperf.com/reduce-vs-native-loop. Performs 80% faster for reduce on chrome. Even if it was even or slower, I'd still prefer those methods for elegancy and convinients.
• jAndy: @spaceman12: I don't see the fail sorry. The original statement was "its way slower", the "slower" part implies a comparison vs. the one other answer to this question, so I'm curios who is failing here. I never stated that a native loop is not faster in general.

Answer 2

use parseFloat() instead of parseInt() to preserve decimal part

for (var i= 0; i< total.length; i++) {
 totalNo += parseFloat(total[i]);
}

Note1: no need to write +(total[i])
Note2: as pointed out by Utkanos, if your array values contain only floating-point values, then parseFloat is not even necessary

• MaxArt: Or NewUser could use +total[i] instead of any parsing function. Let's remember that parseFloat("10px") === 10, and maybe that's not what we want.
• chrisfrancis27: +1 Good point about the unary plus operator - not necessary as parseFloat coerces to a Number.

Answer 3

You dont need either parseInt or parseFloat here. If speed is concerned and for large arrays, used the native loop, it is much faster! however care be be taken as how you code it -

var total = [10, 0.25, 12.75, 1, 0],totalNo=0;
var len=total.length;
for(var i= 0; i<len; i++) 
{
 totalNo = totalNo+total[i];
}

Always note that totalNo+=total[i] is slower than totalNo+total[i]

• jAndy: you can even improve that using a reverse while loop instead.