CODEWITHSUNDEEP
javascript
Rade Ilijev
Rade Ilijev

Reputation: 61

JavaScript Calculate array of objects

I have some struggles calculating inside a for each function with JavaScript. I have one array of objects that looks like this:

[
    {
        "attribute_operator": "*",
        "attribute_value_price": 3
    },
    {
        "attribute_operator": "+",
        "attribute_value_price": 2
    },
    {
        "attribute_operator": "*",
        "attribute_value_price": 2
    }
]

As you see, every value has operator, and there is a starting price, so the real calculation should look like (if starting price is 6 for example):

6 * 3 + 2 * 2

So the output should be in that case 40.

I know how to do it for sum, but how to implement my operator easily?

tried like:

let total = starting_price.value

        calculate_objects.forEach((a: { attribute_value_price: number; }) => {
          total += a.attribute_value_price;
        });

        console.log(total);

Upvotes: 0

Views: 115

Answers (2)

Yash Vora
Yash Vora

Reputation: 1

You can use string literal with eval function. eval function is useful when you want to calculate an expression.

const obj = [
    {
        "attribute_operator": "*",
        "attribute_value_price": 3
    },
    {
        "attribute_operator": "+",
        "attribute_value_price": 2
    },
    {
        "attribute_operator": "*",
        "attribute_value_price": 2
    }
]
let starting_price = 6;
let total = starting_price;

obj.forEach((a) => {
    total =eval(`${total}${a.attribute_operator}${a.attribute_value_price}`) ;
});

console.log(total);

Warning: Executing JavaScript from a string is an BIG security risk.

With eval(), malicious code can run inside your application without permission.

With eval(), third-party code can see the scope of your application, whitch can lead to possible attacks.

Upvotes: -1

danh
danh

Reputation: 62676

This is a good case for reduce. The starting value is that starting_price, and each turn of the loop applies a little function related to the operand...

const starting_price = 6;
const operations = [{
    "attribute_operator": "*",
    "attribute_value_price": 3
  },
  {
    "attribute_operator": "+",
    "attribute_value_price": 2
  },
  {
    "attribute_operator": "*",
    "attribute_value_price": 2
  }
];

const operators = {
  '*': (a, b) => a * b,
  '+': (a, b) => a + b,
};

const result = operations.reduce((acc, el) => {
  let operator = operators[el.attribute_operator];
  let operand = el.attribute_value_price;
  return operator(acc, operand);
}, starting_price);

console.log(result);

Upvotes: 3

Related Questions