Simple Calculator

Goals

• Define a function with multiple parameters
• Use a conditional or match to select the operation
• Return a value from a function
• Handle an edge case (division by zero)

Prerequisites

• Variables and data types (numbers)
• if/else or switch/match statements
• Function definition concept

Steps

2. 1

   Define the function signature

   Create a function calculate(a, op, b) where a and b are numbers and op is a string like "+", "-", "*", "/". The signature tells the caller exactly what to provide.

   CodeCopy

   function calculate(a, op, b) {
     // body comes next
   }

   Expected result

   The function exists and can be called, but returns nothing yet.

4. 2

   Select the operation

   Inside the function, branch on op and perform the matching arithmetic. Returning inside each branch keeps the logic flat and readable.

   CodeCopy

     if (op === "+") return a + b;
     if (op === "-") return a - b;
     if (op === "*") return a * b;
     if (op === "/") return a / b;

   Expected result

   Calling calculate(4, "+", 5) returns 9; calculate(10, "*", 3) returns 30.

6. 3

   Guard division by zero

   Before dividing, check whether b === 0 and return a safe value or message. This prevents Infinity or a runtime error from leaking to the caller.

   CodeCopy

     if (op === "/") {
       if (b === 0) return "Cannot divide by zero";
       return a / b;
     }

   Expected result

   calculate(5, "/", 0) returns the error message instead of Infinity.

   Show hint
8. 4

   Test all operators

   Call the function once for each operator and print the results. Testing every branch is how you confirm the function is complete.

   CodeCopy

   console.log(calculate(4, "+", 5));  // 9
   console.log(calculate(10, "-", 3)); // 7
   console.log(calculate(6, "*", 7));  // 42
   console.log(calculate(8, "/", 2));  // 4
   console.log(calculate(5, "/", 0));  // Cannot divide by zero

   Expected result

   Five lines of output: 9, 7, 42, 4, and the division-by-zero message.

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