Sum values from an array of key-value pairs in JavaScript

Question

I have defined a JavaScript variables called myData which is a new Array like this   var myData   new Array   2013-01-22   0     2013-01-29   0     2013-02-05   0                  2013-02-12   0     2013-02-19   0     2013-02-26   0                   2013-03-05   0     2013-03-12   0     2013-03-19   0                   2013-03-26   0     2013-04-02   21     2013-04-09   2      I am wondering if it is possible to sum the number values found in the array  ex  0 0 21 2 0 and so on  and have probably a variable with the result that I can use outside of the script tag because I have 7 of this kind of arrays corresponding for each of the day in the week  I want to make a comparison afterwards based on that  That is the most preferred method for this kind of actions if is possible

User · Answer

You can use the native map method for Arrays. map Method (Array) (JavaScript)

var myData = new Array(['2013-01-22', 0], ['2013-01-29', 0], ['2013-02-05', 0],
             ['2013-02-12', 0], ['2013-02-19', 0], ['2013-02-26', 0], 
             ['2013-03-05', 0], ['2013-03-12', 0], ['2013-03-19', 0], 
             ['2013-03-26', 0], ['2013-04-02', 21], ['2013-04-09', 2]);
var a = 0;
myData.map( function(aa){ a += aa[1];  return a; });

a is your result

User · Answer

Creating a sum method would work nicely  e g  you could add the sum function to Array  Array prototype sum   function selector        if  typeof selector      function             selector   function item                return item                      var sum   0      for  var i   0  i  lt  this length  i              sum    parseFloat selector this i               return sum       then you could do    gt   1 2 3  sum   6   and in your case   gt  myData sum function item    return item 1       23   Edit  Extending the builtins can be frowned upon because if everyone did it we would get things unexpectedly overriding each other  namespace collisions   you could add the sum function to some module and accept an array as an argument if you like  that could mean changing the signature to myModule sum   function arr  selector    then this would become arr

User · Answer

If you want to discard the array at the same time as summing  you could do  say  stack is the array    var stack    1 2 3       sum   0  while stack length  gt  0    sum    stack pop

User · Answer

Old way  if you don t now the length of arguments parameters     gt  gt  function sumla1         result 0     for let i 0  i lt arguments length i              result  arguments i              return result             gt  gt  sumla1 45 67 88        gt  gt  200   ES6  destructuring of array    gt  gt  function sumla2    x  return x reduce  a b   gt a b    gt  gt   gt  gt  sumla2 5 5 6 7 8   gt  gt   gt  gt  31  gt  gt   gt  gt  var numbers    4  9  16  25    gt  gt  sumla2    numbers    gt  gt  54

User · Answer

You could use the Array reduce method    x000D   x000D  const myData     x000D      2013-01-22   0     2013-01-29   0     2013-02-05   0   x000D      2013-02-12   0     2013-02-19   0     2013-02-26   0    x000D      2013-03-05   0     2013-03-12   0     2013-03-19   0    x000D      2013-03-26   0     2013-04-02   21     2013-04-09   2  x000D     x000D  const sum   myData x000D     map  v   gt  v 1                                    x000D     reduce   sum  current    gt  sum   current  0    x000D     x000D  console log sum   x000D   x000D   x000D    See MDN

User · Answer

I would use reduce  var myData   new Array   2013-01-22   0     2013-01-29   0     2013-02-05   0     2013-02-12   0     2013-02-19   0     2013-02-26   0     2013-03-05   0     2013-03-12   0     2013-03-19   0     2013-03-26   0     2013-04-02   21     2013-04-09   2     var sum   myData reduce function a  b        return a   b 1      0        result   text sum     Available on jsfiddle

User · Answer

I think the simplest way might be   values reduce function a  b  return a b

User · Answer

Or in ES6   values reduce  a  b    gt  a   b    example    1 2 3  reduce  a  b   gt a b     return 6

User · Answer

where 0 is initial value Array reduce  currentValue  value    gt  currentValue  value 0   or Array reduce  currentValue  value    gt   return currentValue  value  0   or  1 3 4  reduce function currentValue  value    return currentValue   value  0

User · Answer

The javascript built-in reduce for Arrays is not a standard  but you can use underscore js   var data     range 10   var sum     data  reduce function memo  i   return memo   i      which becomes   var sumMyData     myData  reduce function memo  i   return memo   i 1    0     for your case  Have a look at this fiddle also

User · Answer

Try the following   x000D   x000D  var myData      2013-01-22   0     2013-01-29   1     2013-02-05   21    x000D   x000D  var myTotal   0      Variable to hold your total x000D   x000D  for var i   0  len   myData length  i  lt  len  i      x000D      myTotal    myData i  1       Iterate over your first array and then grab the second element add the values up x000D    x000D   x000D  document write myTotal      22 in this instance x000D   x000D   x000D

[javascript] Sum values from an array of key-value pairs in JavaScript

Examples related to javascript

Examples related to arrays

Examples related to for-loop

Examples related to sum