How to find the sum of an array of numbers

Question

Given an array  1  2  3  4   how can I find the sum of its elements   In this case  the sum would be 10    I thought   each might be useful  but I m not sure how to implement it

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Use recursion  var sum    arr    gt  arr length     1   arr 0    arr shift     sum arr   sum  1 2 3 4      10

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Funny approach   eval  1 2 3  join

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i saw all answers going for  reduce  solution   var array    1 2 3 4  var total   0 for  var i   0  i  lt  array length  i          total    array i    console log total

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var total   0    each arr function         total    this

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Recommended  reduce with default value   Array prototype reduce can be used to iterate through the array  adding the current element value to the sum of the previous element values    x000D   x000D  console log  x000D     1  2  3  4  reduce  a  b    gt  a   b  0  x000D    x000D  console log  x000D       reduce  a  b    gt  a   b  0  x000D    x000D   x000D   x000D    Without default value  You get a TypeError  x000D   x000D  console log  x000D       reduce  a  b    gt  a   b  x000D    x000D   x000D   x000D    Prior to ES6 s arrow functions   x000D   x000D  console log  x000D     1 2 3  reduce function acc  val    return acc   val     0  x000D    x000D   x000D  console log  x000D       reduce function acc  val    return acc   val     0  x000D    x000D   x000D   x000D    Non-number inputs  If non-numbers are possible inputs  you may want to handle that   x000D   x000D  console log  x000D      hi   1  2   frog   reduce  a  b    gt  a   b  x000D    x000D   x000D  let numOr0   n   gt  isNaN n    0   n x000D   x000D  console log  x000D      hi   1  2   frog   reduce  a  b    gt   x000D      numOr0 a    numOr0 b   x000D    x000D   x000D   x000D    Non-recommended dangerous eval use  We can use eval to execute a string representation of JavaScript code  Using the Array prototype join function to convert the array to a string  we change  1 2 3  into  1 2 3   which evaluates to 6    x000D   x000D  console log  x000D    eval  1 2 3  join       x000D    x000D   x000D    This way is dangerous if the array is built x000D     from user input as it may be exploited eg   x000D   x000D  eval  1  2 alert  Malicious code      join       x000D   x000D   x000D    Of course displaying an alert isn t the worst thing that could happen  The only reason I have included this is as an answer Ortund s question as I do not think it was clarified

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This is much easier  function sumArray arr        var total   0      arr forEach function element           total    element             return total     var sum   sumArray  1 2 3 4    console log sum

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Cool tricks here  I ve got a nit pick with a lot of the safe traditional answers not caching the length of the array   function arraySum array     var total   0        len   array length     for  var i   0  i  lt  len  i         total    array i          return total      var my array    1 2 3 4       Returns 10 console log  arraySum  my array        Without caching the length of the array the JS compiler needs to go through the array with every iteration of the loop to calculate the length  it s unnecessary overhead in most cases   V8 and a lot of modern browsers optimize this for us  so it is less of a concern then it was  but there are older devices that benefit from this simple caching   If the length is subject to change  caching s that could cause some unexpected side effects if you re unaware of why you re caching the length  but for a reusable function who s only purpose is to take an array and add the values together it s a great fit   Here s a CodePen link for this arraySum function  http   codepen io brandonbrule pen ZGEJyV  It s possible this is an outdated mindset that s stuck with me  but I don t see a disadvantage to using it in this context

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You can combine reduce   method with lambda expression    1  2  3  4  reduce  accumulator  currentValue    gt  accumulator   currentValue

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A few people have suggested adding a  sum   method to the Array prototype  This is generally considered bad practice so I m not suggesting that you do it   If you still insist on doing it then this is a succinct way of writing it   Array prototype sum   function    return    reduce call this   a i    gt  a i  0      then   1 2  sum       3  Note that the function added to the prototype is using a mixture of ES5 and ES6 function and arrow syntax  The function is declared to allow the method to get the this context from the Array that you re operating on  I used the   gt  for brevity inside the reduce call

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You can also use reduceRight    1 2 3 4 5 6  reduceRight function a b  return a b      which results output as 21   Reference  https   developer mozilla org en-US docs Web JavaScript Reference Global Objects Array ReduceRight

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This is possible by looping over all items  and adding them on each iteration to a sum-variable   var array    1  2  3    for  var i   0  sum   0  i  lt  array length  sum    array i        JavaScript doesn t know block scoping  so sum will be accesible   console log sum        gt  6   The same as above  however annotated and prepared as a simple function   function sumArray array      for       var       index   0                  The iterator       length   array length      Cache the array length       sum   0                    The total amount       index  lt  length             The  for -loop condition       sum    array index         Add number on each iteration        return sum

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lt  DOCTYPE html gt       lt html gt       lt body gt          lt p gt Click the button to join two arrays  lt  p gt         lt button onclick  myFunction    gt Try it lt  button gt         lt p id  demo  gt  lt  p gt       lt script gt  var hege    1  2 4 6 7 8 8   var stale    1  2 4 5   function myFunction         console log  hege length  gt  stale length           var children     hege length  gt  stale length   abc1    abc2          document getElementById  demo   innerHTML   children    function abc1        console log hege  Abc1           var abcd hege map function  num  idx            console log hege length   idx          return stale length gt idx num   stale idx  num             return abcd     function abc2         console log hege  Abc2  stale          var abcd stale map function  num  idx            console log hege length   idx          return hege length gt idx num   hege idx  num             return abcd     lt  script gt    lt  body gt   lt  html gt

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Those are really great answers  but just in case if the numbers are in sequence like in the question   1 2 3 4  you can easily do that by applying the formula   n  n 1   2 where n is the last number

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In addition  sum with es6 for simple array  const sum    1  2  3  reduce  partial sum  a    gt  partial sum   a 0     console log sum     For object array with default initialize value const totalAmount   obj   gt       Object values obj  reduce  acc    order qty  mrp price      gt       acc   order qty   mrp price  0            console log totalAmount

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var totally   eval arr join         That way you can put all kinds of exotic things in the array   var arr      1 3    Date now     foo   bar    1 2 3 4    I m only half joking

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Accuracy  Sort array and start sum form smallest numbers  snippet shows difference with nonsort       arr  sort  a b   gt a-b  reduce  a c   gt a c 0     x000D   x000D  arr   6 9  1  1  1  1  x000D   x000D  sum                             arr reduce  a c   gt a c 0  x000D  sortSum       arr  sort  a b   gt a-b  reduce  a c   gt a c 0  x000D   x000D  console log  sum        sum   x000D  console log  sortSum   sortSum   x000D  console log  sum  sortSum     sum  sortSum   x000D   x000D     we use  sort  a b   gt a-b  instead  sort   because x000D     that second one treat elements like strings  so in wrong way  x000D     e g  1 10 9 20 93  sort   -- gt    1  10  20  9  93  x000D   x000D   x000D    For multidimensional array of numbers use arr flat Infinity    x000D   x000D  arr       1 2 3 4   1 2 3 4   1 2 3 4     x000D            1 2 3 4   1 2 3 4   1 2 3 4       x000D         x000D  sum   arr flat Infinity  reduce  a c   gt  a c 0   x000D   x000D  console log sum       60 x000D   x000D   x000D

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Here s an elegant one-liner solution that uses stack algorithm  though one may take some time to understand the beauty of this implementation   const getSum   arr   gt   arr length     1    arr 0    arr pop     getSum arr    getSum  1  2  3  4  5     15   Basically  the function accepts an array and checks whether the array contains exactly one item  If false  it pop the last item out of the stack and return the updated array    The beauty of this snippet is that the function includes arr 0  checking to prevent infinite looping  Once it reaches the last item  it returns the entire sum

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In Lisp  this d be exactly the job for reduce  You d see this kind of code    reduce       1 2 3     6   Fortunately  in JavaScript  we also have reduce  Unfortunately    is an operator  not a function  But we can make it pretty  Here  look   const sum    1  2  3  reduce add 0      with initial value to avoid when the array is empty  function add accumulator  a        return accumulator   a     console log sum      6   Isn t that pretty   -   Even better  If you re using ECMAScript nbsp 2015  aka ECMAScript nbsp 6   it can be this pretty   const sum    1  2  3  reduce  partial sum  a    gt  partial sum   a 0    console log sum      6

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try this     function arrSum arr       total   0        arr forEach function key           total   total   key                          return total

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Use reduce   x000D   x000D  let arr    1  2  3  4   x000D   x000D  let sum   arr reduce  v  i    gt   v   i    x000D   x000D  console log sum   x000D   x000D   x000D

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Why not reduce  It s usually a bit counter intuitive  but using it to find a sum is pretty straightforward   var a    1 2 3   var sum   a reduce function a  b    return a   b     0

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A standard JavaScript solution   var addition       addition push 2   addition push 3    var total   0  for  var i   0  i  lt  addition length  i          total    addition i     alert total               Just to output an example    console log total      Just to output an example with Firebug      This works for me  the result should be 5   I hope there is no hidden disadvantage in this kind of solution

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A short piece of JavaScript code would do this job   var numbers    1 2 3 4   var totalAmount   0   for  var x   0  x  lt  numbers length  x           totalAmount    numbers x      console log totalAmount     10  1 2 3 4

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Use map   var sum   0  arr map function item       sum    item          sum now contains the total    You could potentially add the method to the Array prototype   Array prototype sum   function        var sum   0      this map function item           sum    item              return sum      Then you can use it on any Array like so   arr sum

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Given array  arr  var i   arr length  var sum   0  while  --i  sum    arr i     This will take on average 1 57 ms run  measured over 1000 runs on an array of 100 random normal numbers   compared to 3 604 ms run with the eval   method above and 2 151 ms run with a standard for i length     loop   Methodology note  this test was run on a Google Apps Script server  so their javascript engines are pretty much the same as Chrome   EDIT  --i instead of i-- saves 0 12 ms each run  i-- is 1 7   EDIT  Holy expletive  never mind this whole post  Use the reduce   method mentioned above  it s only 1 ms run

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Just use this function   function sum pArray      pArray   pArray reduce function  a  b          return a   b       0      return pArray       x000D   x000D  function sum pArray  x000D    x000D    pArray   pArray reduce function  a  b    x000D        return a   b  x000D       0   x000D   x000D    return pArray  x000D    x000D   x000D  var arr    1  4  5   x000D   x000D  console log sum arr    x000D   x000D   x000D

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arr reduce function  a  b        return a   b        Reference  Array prototype reduce

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Use a for loop   const array    1  2  3  4   let result   0   for  let i   0  i  lt  array length - 1  i        result    array i      console log result      Should give 10   Or even a forEach loop   const array    1  2  3  4   let result   0   array forEach number   gt      result    number      console log result      Should give 10   For simplicity  use reduce   const array    10  20  30  40   const add    a  b    gt  a   b const result   array reduce add    console log result      Should give 100

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When the array consists of strings one has to alter the code  This can be the case  if the array is a result from a databank request  This code works   alert    1    2    3    4   reduce  a  b    gt  Number a    Number b   0       Here    1    2    3    4   ist the string array and the function Number   converts the strings to numbers

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No need to initial value  Because if no initial value is passed  the callback function is not invoked on the first element of the list  and the first element is instead passed as the initial value  Very cOOl feature      1  2  3  4  reduce  a  x    gt  a   x     10  1  2  3  4  reduce  a  x    gt  a   x     24  1  2  3  4  reduce  a  x    gt  Math max a  x      4  1  2  3  4  reduce  a  x    gt  Math min a  x      1

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This function can sum up all the numbers -   function array arr      var sum   0     for  var i   0  i lt  arr length  i         sum    arr i           console log sum       array  5  1  3  3

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Anyone looking for a functional oneliner like me  Take this  sum   arr reduce  a  b    gt  a   b  0     If you happen to have to support ye olde IE without arrow functions   sum   arr reduce function  a  b   return a   b    0

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If you happen to be using Lodash you can use the sum function  array    1  2  3  4   sum     sum array      sum    10

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Considering you have the array const arr    1  2  3  4    For me  the most intuitive way is using a for-in let sum   0  for var value in arr        sum    arr value      console log  Array    arr   console log  Sum    sum    Yet  you can also use Arrow Functions and the reduce function const sum   arr reduce function  a  b        return a   b     0    console log  Array    arr   console log  Sum    sum    They re both gonna output Array    1  2  3  4  Sum  10

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A  duplicate  question asked how to do this for a two-dimensional array  so this is a simple adaptation to answer that question   The difference is only the six characters  2   0  which finds the third item in each subarray and passes an initial value of zero     x000D   x000D  const twoDimensionalArray     x000D     10  10  1   x000D     10  10  2   x000D     10  10  3   x000D     x000D  const sum   twoDimensionalArray reduce   partial sum  a    gt  partial sum   a 2   0      x000D  console log sum      6 x000D   x000D   x000D

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Vanilla JavaScript is all you need    gt  a    1 2 3 4   a foo   5  a  bar     6  sum   0  a forEach function e  sum    e    sum 10  gt  a    1 2 3 4   a foo   5  a  bar     6  sum   0  a forEach e   gt  sum    e   sum 10  gt  a    1 2 3 4   a foo   5  a  bar     6  sum   0  for e in a  sum    e  sum  00123foobar   gt  a    1 2 3 4   a foo   5  a  bar     6  sum   0  for e of a  sum    e  sum 10

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You can try this  var arr    100 114 250 1200   var total   0   for var i in arr     total    parseInt arr i       console log total    Output will be  1664 Or if value is Float  then try this  var arr    100 00 114 50 250 75 1200 00       var total   0       for var i in arr         total    parseFloat arr i                   console log total toFixed 2     Output will be  1665 25

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OK  imagine you have this array below   const arr    1  2  3  4     Let s start looking into many different ways to do it as I couldn t find any comprehensive answer here   1  Using built-in reduce    function total arr      if  Array isArray arr   return    return arr reduce  a  v   gt a   v       2  Using for loop  function total arr      if  Array isArray arr   return    let totalNumber   0    for  let i 0 l arr length  i lt l  i           totalNumber  arr i         return totalNumber      3  Using while loop  function total arr      if  Array isArray arr   return    let totalNumber   0  i -1    while    i  lt  arr length         totalNumber  arr i         return totalNumber      4  Using array forEach  function total arr      if  Array isArray arr   return    let sum 0    arr forEach each   gt        sum  each          return sum       and call it like this   total arr     return 10   It s not recommended to prototype something like this to Array

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For really large numbers cycling or reducing could be process intensive  What about using Gauss   sum    n    n 1   2    From mathcentral

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A simple method example   function add array       var arraylength   array length      var sum   0      for var timesToMultiply   0  timesToMultiply lt arraylength  timesToMultiply             sum    array timesToMultiply              return sum     console log add  1  2  3  4

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With ES6 rest parameter   x000D   x000D  let array    1  2  3  4  x000D   x000D  function sum    numbers    x000D      let total   0  x000D      for  const number of numbers    x000D          total    number  x000D        x000D      return total  x000D    x000D   x000D  console log sum    array    x000D   x000D   x000D

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ES6 for  of let total   0   for  let value of  1 2 3 4         total    value

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Object defineProperty Object prototype   sum         enumerable false      value function             var t 0 for var i in this              if   isNaN this i                    t  this i           return t              20 25 27 1  sum                      72 1  10  forty-two  23  sum               33  Math PI 0 -1 1  sum                  3 141592653589793  Math PI Math E -1000000000  sum      -999999994 1401255  o    a 1 b 31 c  roffelz  someOtherProperty 21 52  console log o sum                     53 519999999999996

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var arr    1 2 3 4   var total 0  for var i in arr    total    arr i

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I am a beginner with JavaScript and coding in general  but I found that a simple and easy way to sum the numbers in an array is like this        var myNumbers    1 2 3 4 5      var total   0      for var i   0  i  lt  myNumbers length  i             total    myNumbers i           Basically  I wanted to contribute this because I didn t see many solutions that don t use built-in functions  and this method is easy to write and understand

[javascript] How to find the sum of an array of numbers

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