Calculate sum of elements in an array within a function

Question

I'm doing a prework for a course I'm going to attend and I have to complete some ex. I started learning JS last week so I'm a newbie and in this ex I don't have to use any method that allows me to calculate the sum. I only have to use logic. (for loops-functions-switch)

This is the ex: Define a function that will receive an array as an argument and calculate a sum of all its elements. For example, if we pass the following array to that function: const prices = [5, 7.99, 9.99, 0.99, 21], it should return 44.97 as output. How would you concatenate $ sign in front of the sum?

I don't really know how to do that sum, in fact the code I've written is totally wrong but I'd like to understand the logic behind.

function calculator (someArray) {
  let result;
  for(let i=0; i<= someArray.length; i++) {
    console.log(someArray[i]);
  }
  result=someArray[i] + someArray[i+=1];
}

const prices = [5, 7.99, 9.99, 0.99, 21];

calculator(prices);

I've now changed the code but it only prints the first 2 elements of the array:

function calculator (someArray) {
  let result;
  for(let i = 0; i<= someArray.length; i++) {
    result = someArray[i] + (someArray[i+=1]);
    console.log(result);
    return result;
  }
}

const prices = [5, 7.99, 9.99, 0.99, 21];

calculator(prices);

Your code is not working, there is a mismatched parenthesis and you didn't return the result in calculator function. — Hao Wu
– Hao Wu, Commented Sep 11, 2020 at 9:29
Great start. Not only you have coded something but you asked the question very well. Regarding the code itself: you have an offset-by-one error (actually 2) , which is not executed because of your premature return. But this is normal, just keep going (y) — malarres
– malarres, Commented Sep 11, 2020 at 9:50
you are going outside of the array twice: once with "<=" and the second time(s) with "i+1" - I think... The for loop increments i, so there is no need to increment inside of it. See my answer for a few ways of doing sum... — iAmOren
– iAmOren, Commented Sep 11, 2020 at 10:17

malarres · Accepted Answer · 2020-09-11 10:13:24Z

This is the ex: Define a function that will receive an array as an argument and calculate a sum of all its elements. For example, if we pass the following array to that function: const prices = [5, 7.99, 9.99, 0.99, 21], it should return 44.97 as output. How would you concatenate $ sign in front of the sum?

Javascript has a nice feature: reduce

function calculator (someArray){
  return someArray.reduce((howMuchSoFar,currentElementOfTheArray) => {
    howMuchSoFar = howMuchSoFar + currentElementOfTheArray;
    return howMuchSoFar;
  });
}

const prices = [5, 7.99, 9.99, 0.99, 21];

console.log("$"+calculator(prices));

(intentionally verbose)

Going back to your original code (a classic for loop)

arrays go from 0 to length-1, control that
whathever[i+=1] is actually doing two things: i=i+1 and bringing whatever[i] , it is better going step by step for now, and inside the loop you're already doing i++ so this won't be good
return is for the whole function, not for each step of a classic for. If needed, go with break, but please understand firstly the while loop

function calculator (someArray){
  let result=0;
  for( let i = 0; i< someArray.length; i++){  
    result = result + someArray[i];
  }
  return result;
}

const prices = [5, 7.99, 9.99, 0.99, 21];

console.log("$"+calculator(prices));

iAmOren · Accepted Answer · 2020-09-11 10:18:23Z

function calculator1(someArray) {
  let result=0;
  for(let i=0; i<someArray.length; i++) {
    result=result+someArray[i];
  }
  return result;
}

function calculator2(someArray) {
  let result=0;
  for(let i=0; i<someArray.length; i++) {
    result+=someArray[i];
  }
  return result;
}

function calculator3(someArray) {
  return someArray.reduce((accumulator, currentValue)=>accumulator+currentValue,0);
}

const prices=[5, 7.99, 9.99, 0.99, 21];

console.log("calculator1: "+calculator1(prices));
console.log("calculator2: "+calculator2(prices));
console.log("calculator3: "+calculator3(prices));

let sumWithDollarSign="$"+calculator3(prices);
console.log("sumWithDollarSign: "+sumWithDollarSign);

calculator1 is straight-forward JavaScript.
calculator2 uses += which means: add the right side to the left.
calculator3 uses Array.reduce with accumulator starting with value 0, iterating over all items in Array - each is in currentValue, and adding to accumulator and returning it at the end.

"$"+someNumber concatenates the two. Enough that one of the 2 (or more) is a String to return a String.

Ashish Mishra · Accepted Answer · 2020-09-11 09:29:48Z

0

Syntax error

replace this

     result = someArray[i] + (someArray[i+=1];

with

     result = someArray[i] + (someArray[i+=1]);

answered Sep 11, 2020 at 9:29

Ashish Mishra

4264 silver badges7 bronze badges

Comments

Greg Rowles · Accepted Answer · 2024-08-23 13:49:19Z

0

This is dirty but works:

const prices = [5, 7.99, 9.99, 0.99, 21];

console.log( eval( prices.toString().replace(/,/g,'+' ) ) );

answered Aug 23, 2024 at 13:49

Greg Rowles

3413 silver badges14 bronze badges

Collectives™ on Stack Overflow

Calculate sum of elements in an array within a function

4 Answers 4

Comments

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related