Simple calculator Lambda function - Amazon API Gateway

# Simple calculator Lambda function

As an illustration, we will use a Node.js Lambda function that performs the binary operations of addition, subtraction, multiplication and division.

## Simple calculator Lambda function input format

This function takes an input of the following format:

``{ "a": "Number", "b": "Number", "op": "string"}``

where `op` can be any of `(+, -, *, /, add, sub, mul, div)`.

## Simple calculator Lambda function output format

When an operation succeeds, it returns the result of the following format:

``{ "a": "Number", "b": "Number", "op": "string", "c": "Number"}``

where `c` holds the result of the calculation.

## Simple calculator Lambda function implementation

The implementation of the Lambda function is as follows:

``````export const handler = async function (event, context) {

if (
event.a === undefined ||
event.b === undefined ||
event.op === undefined
) {
return "400 Invalid Input";
}

const res = {};
res.a = Number(event.a);
res.b = Number(event.b);
res.op = event.op;
if (isNaN(event.a) || isNaN(event.b)) {
return "400 Invalid Operand";
}
switch (event.op) {
case "+":
res.c = res.a + res.b;
break;
case "-":
case "sub":
res.c = res.a - res.b;
break;
case "*":
case "mul":
res.c = res.a * res.b;
break;
case "/":
case "div":
if (res.b == 0) {
return "400 Divide by Zero";
} else {
res.c = res.a / res.b;
}
break;
default:
return "400 Invalid Operator";
}

return res;
};``````