<\/span><\/h2>\n\n\n\nThis is the simplest way to sum items in an array. We initialize the sum of array to zero in a variable. Then we run a for loop over the array items and in each iteration we add the item to the sum. By the time the for loop exits, the sum variable will contain the value of sum of array items.<\/p>\n\n\n\n
Here is an example to illustrate it.<\/p>\n\n\n\n
var array = [1, 2, 3, 4, 5];
var sum = 0;
for (i = 0; i < array.length; i++) {
sum += array[i];
}
console.log(sum); \/\/ output is 15 <\/pre>\n\n\n\nThis method is very easy to understand and applicable for all arrays. You can also selectively choose the items you want to include\/exclude in the sum, by adding custom conditions in each iteration. Here is an example to sum only even numbers in an array.<\/p>\n\n\n\n
var array = [1, 2, 3, 4, 5];
var sum = 0;
for (i = 0; i < array.length; i++) {
if(array[i]%2 == 0){
sum += array[i];
}
}
console.log(sum); \/\/ output is 6<\/pre>\n\n\n\nIf your data contains non-numerical items then you can call a custom function to use 0 in its place, in every iteration. Here is an example where define a function isnum() to simply check if a variable is a number or not. If it is not a number, the function returns 0, else it returns the number itself.<\/p>\n\n\n\n
var array = [1, 'a', 3, 'b', 5];
var sum = 0;
function isnum(n){
return isNaN(n) ? 0 : n;
}
for (i = 0; i < array.length; i++) {
sum += isnum(array[i]);
}
console.log(sum); \/\/ output is 9<\/pre>\n\n\n\nYou can always define a function that accepts an array as an input argument and runs a for loop to calculate the sum of its elements.<\/p>\n\n\n\n
var a = [1, 2, 3, 4, 5];
function sum(array){
var sum = 0;
for (i = 0; i < array.length; i++) {
sum += array[i];
}
return sum;
}
console.log(sum(a)); \/\/ output is 15 <\/pre>\n\n\n\nYou may also use other loop constructs like while to loop through the array and find sum of its elements.<\/p>\n\n\n\n