How do I print the return value on the console?-CodePudding

I've got a course task to make a calculator in Javascript. I've got the functions for the different operators and the case-switch but I'm struggling with how to print the return values of the functions. Here's the code I've got so far:

let firstValue = prompt("Enter a number");

let secondValue = prompt("Enter a second number");

let operation = prompt("How should these numbers interact");

function addition(firstValue, secondValue) {
  return firstValue   secondValue;
}

function subtraction(firstValue, secondValue) {
  return firstValue - secondValue;
}

function division(firstValue, secondValue) {
  return firstValue / secondValue;
}

function multiplication(firstValue, secondValue) {
  return firstValue * secondValue;
}

function powerTo(firstValue, secondValue) {
  return firstValue ^ secondValue;
}

switch (operation) {
  case " ":
    addition();
    break;
  case "-":
    subtraction();
    break;
  case "/":
    division();
    break;
  case "*":
    multiplication();
    break;
  case "^":
    powerTo();
    break;
  default:
    console.log("No operation inputted");
    break;
}

console.log(`${firstValue} ${operation} ${secondValue} =`)

CodePudding user response：

Assign the result of calling the operation function to a variable, then display that in the console.

You also need to pass arguments to all the functions.

And you should convert the input to a number before using it in calculations. Most of the arithmetic operators will convert it automatically, but will do string concatenation.

let firstValue = Number(prompt("Enter a number"));

let secondValue = Number(prompt("Enter a second number"));

let operation = prompt("How should these numbers interact");

function addition(firstValue, secondValue) {
  return firstValue   secondValue;
}

function subtraction(firstValue, secondValue) {
  return firstValue - secondValue;
}

function division(firstValue, secondValue) {
  return firstValue / secondValue;
}

function multiplication(firstValue, secondValue) {
  return firstValue * secondValue;
}

function powerTo(firstValue, secondValue) {
  return firstValue ^ secondValue;
}

let result;

switch (operation) {
  case " ":
    result = addition(firstValue, secondValue);
    break;
  case "-":
    result = subtraction(firstValue, secondValue);
    break;
  case "/":
    result = division();
    break;
  case "*":
    result = multiplication(firstValue, secondValue);
    break;
  case "^":
    result = powerTo(firstValue, secondValue);
    break;
  default:
    console.log("No operation inputted");
    break;
}

console.log(`${firstValue} ${operation} ${secondValue} = ${result}`)

CodePudding user response：

There are a couple of things wrong with your code. First you need to save the result of the function call to a variable, second you need to pass the arguments to the function and finally in javascript exponents are done using the ** operator not the ^ operator, ^ is used for a bitwise xor.

Here is your code when it is fixed:

let firstValue = prompt("Enter a number");

let secondValue = prompt("Enter a second number");

let operation = prompt("How should these numbers interact");


function addition(firstValue, secondValue) {
    return firstValue   secondValue;
}

function subtraction(firstValue, secondValue) {
    return firstValue - secondValue;
}

function division(firstValue, secondValue) {
   return firstValue / secondValue;
}

function multiplication(firstValue, secondValue) {
    return firstValue * secondValue;
}

function powerTo(firstValue, secondValue) {
    return firstValue ** secondValue;
}

let result;
switch(operation) {
    case " " :
        result = addition(firstValue, secondValue);
        break;
    case "-":
        result = subtraction(firstValue, secondValue);
        break;
    case "/":
        result = division(firstValue, secondValue);
        break;
    case "*":
        result = multiplication(firstValue, secondValue);
        break;
    case "^":
        result = powerTo(firstValue, secondValue);
        break;
    default:
        console.log("No operation inputted");
        break;
}

console.log(`${firstValue} ${operation} ${secondValue} = ${result}`);

However in this case I feel that separating the operations into functions is unnecessary. Here is a cleaned up version:

let firstValue = prompt("Enter a number");

let secondValue = prompt("Enter a second number");

let operation = prompt("How should these numbers interact");

let result;
switch(operation) {
    case " " :
        result = firstValue   secondValue;
        break;
    case "-":
        result = firstValue - secondValue;
        break;
    case "/":
        result = firstValue / secondValue;
        break;
    case "*":
        result = firstValue * secondValue;
        break;
    case "^":
        result = firstValue ** secondValue;
        break;
    default:
        console.log("No operation inputted");
        break;
}

console.log(`${firstValue} ${operation} ${secondValue} = ${result}`);

CodePudding user response：

EDIT: everyone answered at the same time with the same thing so I thought I would spice my answer up with some unsafe code

const firstValue = prompt("Enter a number");

const secondValue = prompt("Enter a second number");

const operation = prompt("How should these numbers interact");

const expression = `${firstValue} ${operation} ${secondValue}`;

const result = eval(expression);

console.log(`${expression} = ${result}`);

CodePudding user response：

Another way of solving the problem. More complicated, but safe and clean.

function getNumber(message) {
    let number;
    do {
        number = prompt(message);
        if (isNaN(number)) {
            alert(`${number} is not a number, try again.`);
        } else break;
    } while (true);
    return parseInt(number);
}

function add(offset, x) {
    return offset   x;
}

const operations = {
    " ": add,
};

const firstNumber = getNumber("Enter the first number");
const secondNumber = getNumber("Enter the second number");

let operation;
do {
    operation = prompt("How should these numbers interact");
    if (!operations[operation]) {
        alert(operation   " is not supported");
    } else break;
} while (true);

const calculate = operations[operation];

const result = calculate(firstNumber, secondNumber);
alert("Answer is "   result);