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I am simulating a calculator using Javascript.

Where a user can input 2 numbers in a given text box, and it will display sum, product, difference and division.

Here is my function-

function calculate(num1, num2) {
  console.log("First Number = " + num1 + " Second Number = " + num2);
  console.log("Sum = " + (num1 + num2));
  console.log("Product =" + (num1 * num2));
  console.log("Difference = " + (num1 - num2));
  console.log("Division = " + (num1 / num2));
}

When user inputs 1st number 4 and second number 3 i get this result:

First Number = 4 Second Number = 3
Sum = 43  // sum should be 7 NOT 43
Product = 12 
Difference = 1 
Division = 1.3333333333333333 

Any ideas what is wrong here?

I am simulating a calculator using Javascript.

Where a user can input 2 numbers in a given text box, and it will display sum, product, difference and division.

Here is my function-

function calculate(num1, num2) {
  console.log("First Number = " + num1 + " Second Number = " + num2);
  console.log("Sum = " + (num1 + num2));
  console.log("Product =" + (num1 * num2));
  console.log("Difference = " + (num1 - num2));
  console.log("Division = " + (num1 / num2));
}

When user inputs 1st number 4 and second number 3 i get this result:

First Number = 4 Second Number = 3
Sum = 43  // sum should be 7 NOT 43
Product = 12 
Difference = 1 
Division = 1.3333333333333333 

Any ideas what is wrong here?

• javascript
• html
• input
• numbers
• addition

Share Improve this question Follow asked Oct 10, 2014 at 22:02 AshimaAshima 4,83466 gold badges4141 silver badges6464 bronze badges 4

• 1 They are being treated as strings because you are concatenating them. Try using parseInt(). – Goose Commented Oct 10, 2014 at 22:04
• but other operation work fine. It divides correct, subtracts correct, and multiplies correct – Ashima Commented Oct 10, 2014 at 22:05
• Because + is also used to concatenate strings, and it will do that if any part of the equation is a string. – Goose Commented Oct 10, 2014 at 22:06
• Just make sure string is not passed as parameters instead of numbers like calculate('4','3').Your code gives 7 if it is called with calculate(4,3)...It is giving 7 without parseInt for me.Tested in chrome and firefox – AL-zami Commented Oct 11, 2014 at 0:07

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4 Answers 4

Sorted by: Reset to default 6

Because + is also a String Concatinater in JavaScript. use parseInt(var1) + parseInt(var2) it will work. also have a look on ---> Javascript Operators

to understand the + operator. Thanks

If you're taking in the numbers in a text box they're treated as strings, so the + operator will do string concatenation. The * operator doesn't mean anything in relation to strings, so the javascript engine will try to interpret the inputs as numbers.

You can use parseInt on the inputs to convert them to numbers, or use the html number input type.

try

console.log("Sum = " + (parseInt(num1) + parseInt(num2)));

or

console.log("Sum = " + (0 + num1 + num2));

also make sure you are calling the function like

calculate(4, 3);

and not

calculate('4', '3');

At least one of your inputs to calculate() is string. + is defined for string so bee 43. While */- are not defined for string and Javascript "cleverly" convert them to int.

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