Having trouble finding the sum of values in an array using the Reduce method?

Question

Having trouble finding the sum of values in an array using the Reduce method?

I have always used a 'for' loop to calculate sums in tables, but recently I learned about a better way - using the 'reduce' method. Following documentation and examples with simple arrays was easy enough, but now I am working with an array of objects. Here is my code, and I know there must be a simple mistake that I'm overlooking:

let dataRevenus = [
    { id: 1, label: intl.get("REVENUES_FONCIERS"), value: 230000000 },
    { id: 2, label: intl.get("REVENUES_VALUERS_MOBILIERES"), value: 25000000 },
    { id: 3, label: intl.get("PENSIONS_RETRAITES"), value: 33008.0 }
];

let test = 0;
let sum = dataRevenus
    ? dataRevenus.reduce((acc, item) => {
            console.log("here : " + parseFloat(item.value));

            test = test + parseFloat(item.value);

            return test;
      })
    : 0;

console.log(sum);

My console output shows that the first item is not being included in the calculation. This is the result I get:

here : 25000000
here : 33008
25033008

Despite getting the correct total sum, it seems like I'm missing out on including the value of the first item

Any assistance or advice would be greatly appreciated

javascript arrays reduce

Answer 1

Answer №1

you might want to try a different approach with the reduce method, here's a sample code that could work for you:

let dataRevenus = [
    { id: 1, label: intl.get("REVENUES_FONCIERS"), value: 230000000 },
    { id: 2, label: intl.get("REVENUES_VALUERS_MOBILIERES"), value: 25000000 },
    { id: 3, label: intl.get("PENSIONS_RETRAITES"), value: 33008.0 }
];
let sum = dataRevenus
    ? dataRevenus.reduce((acc, item) => {
            console.log("here : " + parseFloat(item.value));
            return acc + item.value;
      }, 0)
    : 0;

console.log(sum);

You might want to consider adding an initializer for the accumulator. Also, as @VLAZ pointed out, be cautious about using external variables in your code.

If you'd like to see this code in action, check it out on jsfiddle: https://jsfiddle.net/5uspgwL8/

An updated version of the original code with the initializer added (and the intl variable): https://jsfiddle.net/weomztad/

For more information, refer to the explanation provided by @Ivar in this link.

Answer 2

you might want to try a different approach with the reduce method, here's a sample code that could work for you:

let dataRevenus = [
    { id: 1, label: intl.get("REVENUES_FONCIERS"), value: 230000000 },
    { id: 2, label: intl.get("REVENUES_VALUERS_MOBILIERES"), value: 25000000 },
    { id: 3, label: intl.get("PENSIONS_RETRAITES"), value: 33008.0 }
];
let sum = dataRevenus
    ? dataRevenus.reduce((acc, item) => {
            console.log("here : " + parseFloat(item.value));
            return acc + item.value;
      }, 0)
    : 0;

console.log(sum);

You might want to consider adding an initializer for the accumulator. Also, as @VLAZ pointed out, be cautious about using external variables in your code.

If you'd like to see this code in action, check it out on jsfiddle: https://jsfiddle.net/5uspgwL8/

An updated version of the original code with the initializer added (and the intl variable): https://jsfiddle.net/weomztad/

For more information, refer to the explanation provided by @Ivar in this link.

Answer 3

Answer №2

The reduce method is a powerful tool for aggregating data in an array using a custom function and an optional initial value:

array.reduce(function(x, y), [initialValue])

When the initial value is not provided (as in your case), the function starts with the first and second elements of the array as arguments. This means that when using item as the second argument in your function, the expression you supplied

test = test + parseFloat(item.value);

will begin with the second element of the array. The beauty of this method is that it automatically passes the total value from one iteration to the next, eliminating the need for an external variable to store the sum.

Answer 4

The reduce method is a powerful tool for aggregating data in an array using a custom function and an optional initial value:

array.reduce(function(x, y), [initialValue])

When the initial value is not provided (as in your case), the function starts with the first and second elements of the array as arguments. This means that when using item as the second argument in your function, the expression you supplied

test = test + parseFloat(item.value);

will begin with the second element of the array. The beauty of this method is that it automatically passes the total value from one iteration to the next, eliminating the need for an external variable to store the sum.

Having trouble finding the sum of values in an array using the Reduce method?

Answer №1

Answer №2

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