Sum of a javascript array returns a string concatenation of all the numbers [closed]

Answer 1

Array elements are strings, in order to properly add them, they have to be casted to integer:

var sum = tot.reduce(function(a, b) {
  return parseFloat(a) + parseFloat(b);
}, 0);

Taken from MDN:

the concatenation operator (+) concatenates two string values together, returning another string that is the union of the two operand strings.

The is a common issue caused by + operator used for both string concatenation and addition. Issue is best described with following example:

var result = '1' + 3 + 3 + 7 //result is '1337'

Edit: @Pointy - Nice catch, thanks! :)

Answer 2

you will need to use a parse int because its concatenating the sting instead of adding integers

var sum = tot.reduce(function(pv, cv) { return parseInt(pv) + parseInt(cv); }, 0);

parseInt

Answer 3

You have to use parseInt (if the numbers are Integers), parseFloat (if they are Floats) or Number (if not sure) to explicitly interpret them as numbers like:

sum = tot.reduce((a, n) => (a + Number(n)), 0);