how can take sum of array element using javascript?

Question

I have a Array

 var Mark = [1,2,3,4,5];

& I want following results after applying javascript

var result=15;

Am using for loop

var result= 0;
for(var i = 0; i < Mark.length; i++)
{
    result += Mark[i];
}

this code correct or not,
I'm sure there is a better way then straight iteration,
anyone please help me

Answer 1

The most fastest way will probably be using a simple loop as you created.

Here's a different approach using Array.Reduce:

var sum = Mark.reduce(function(prev, curr) { return prev + curr; }, 0);

Answer 2

var Mark = [1, 2, 3, 4, 5], sum = 0, l = Mark.length;

while (l--) sum += Mark[l];

console.log('sum is: ', sum);

open console...

Answer 3

It's fastest if you cache the array's length and then do a reverse loop on it:

var arr = [1,2,3],
    sum = 0,
    i   = arr.length;

while( i-- )
    sum += arr[i];  // 6

Answer 4

This a bit playing with words, but if your array is actually only made of consecutive integers starting from 0 to m or more generally from n to m with a constant common difference d (or step if you prefer), you can do something which is both better and faster ;)

In the case you described

var n = 1;
var m = 5; // (the length of your array)
var d = 1; // you increment with for each element
// n m and d describe [1,2,3,4,5]

var sum = ((m * (m + 1) / 2) - ((n - 1) * n / 2)) * d;

No looping needed, but this works only with matching problems for arithmetic progression

Joke aside, looping is generally a good thing, as long as you don't nest too much of them depending on the same variables boundaries.

Answer 5

I recommend you to take a look to underscore

http://underscorejs.org/

This library will make your live easier in javascript.

And this is how you make a sum with it

var Mark = [1,2,3,4,5];
var sum = _.reduce(Mark, function(memo, num){ return memo + num; }, 0);

Answer 6

try this

var result= 0;
 for(var i = 0; i < Mark.length; i++)
 {
    result+= Mark[i];
 }