How can I sum up a list of numbers inside a variable which I generated inside a forEach loop

Question

I have made a for each loop to access numbers from a JSON array, the array will be dynamic and forever changing and so I have isolated the numbers inside a variable (the variable is inside the loop). My question is: How do I sum up the numbers that are in the variable.

I tried doing a for loop inside the loop but it didn't work.

it looks kind of like this:

 const arrayhours = Array.from(json_obj); arrayhours.forEach(e=>{ const hours = parseFloat(e.hoursWorked); console.log(hours); //returns for example 1.25 9 5 8 7 as seperate objects. });

image of console log

let sum = arrayhours.reduce((a, c) => a + +c.hoursWorked, 0); — arizafar
– arizafar, Commented Jan 23, 2020 at 11:50

Jins Thomas Shaji · Accepted Answer · 2020-01-23 12:07:02Z

2

You can use Array.reduce() for getting sum of numbers in an array.

const arrayhours = Array.from(json_obj); arrayhours.forEach(e=>{ const hours = parseFloat(e.hoursWorked); console.log(hours); //returns for example 1.25 9 5 8 7 as seperate objects. }); const sum = arrayhours.reduce((acc, val) => acc + parseFloat(val.hoursWorked), 0)

answered Jan 23, 2020 at 12:07

Jins Thomas Shaji

8775 silver badges16 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Ingimar Eyfjord Smarason Over a year ago

That works perfectly, however, I left out one argument, I didn't think it would matter but in this case it does. I have an if argument that narrows down the const "hours" down to hours that are worked inside that period. arrayhours.forEach(e=>{ if(e.UnixTimestamp >= startselect && e.UnixTimestamp <= endselect){ const hours = parseFloat(e.hoursWorked); console.log(hours); //returns for example 1.25 9 5 8 7 as seperate objects. } }) const sum = arrayhours.reduce((acc, val) => acc + parseFloat(val.hoursWorked), 0) console.log(sum); will return sum of entire set in json

Ingimar Eyfjord Smarason Over a year ago

Your answer led me to the solution, thanks for the help.

Lux · Accepted Answer · 2020-01-23 12:09:27Z

Initialize the variable with let hours = 0 before the loop and then use += to add something (instead of =) to assign something.

Finally move the console.log out of the loop:

const arrayhours = Array.from(json_obj); let hours = 0; arrayhours.forEach(e => { const hours += parseFloat(e.hoursWorked); }); console.log(hours);

Alexandre_Cbt · Accepted Answer · 2020-01-23 12:12:38Z

const sum = arrayhours.reduce((acc, curr) => acc + parseFloat(curr.hoursWorked, 10), 0)

In comment, AZ_ is using +c.hoursWorked which is a JS trick to cast (if possible) a string into an Int. It is a pretty bad way to to dit, because not really readable. Better use parseInt or parseFloat functions.

Collectives™ on Stack Overflow

How can I sum up a list of numbers inside a variable which I generated inside a forEach loop

3 Answers 3

2 Comments

Comments

Comments

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

2 Comments

Comments

Comments

Related