# Programming Fundamentals/Conditions/JavaScript

## conditions.js

```// This program asks the user to select Fahrenheit or Celsius conversion
// and input a given temperature. Then the program converts the given
// temperature and displays the result.
//
// References:
//   https://www.mathsisfun.com/temperature-conversion.html
//   https://en.wikibooks.org/wiki/JavaScript

main();

function main()
{
// main could either be an if-else structure or a switch-case structure

var choice;
var temperature;
var result;

choice = getChoice();

// if-else approach
if (choice == "C" || choice == "c") {
temperature = getTemperature("Fahrenheit");
result = calculateCelsius(temperature);
displayResult(temperature, "Fahrenheit", result, "Celsius");
}
else if (choice == "F" || choice == "f") {
temperature = getTemperature("Celsius");
result = calculateFahrenheit(temperature);
displayResult(temperature, "Celsius", result, "Fahrenheit");
}
else {
output("You must enter C to convert to Celsius or F to convert to Fahrenheit!");
}

// switch-case approach
switch(choice) {
case 'C':
case 'c':
temperature = getTemperature("Fahrenheit");
result = calculateCelsius(temperature);
displayResult(temperature, "Fahrenheit", result, "Celsius");
break;
case 'F':
case 'f':
temperature = getTemperature("Celsius");
result = calculateFahrenheit(temperature);
displayResult(temperature, "Celsius", result, "Fahrenheit");
break;
default:
output("You must enter C to convert to Celsius or F to convert to Fahrenheit!");
}
}

function getChoice() {
var choice;

output("Enter C to convert to Celsius or F to convert to Fahrenheit:");
choice = input();

return choice;
}

function getTemperature(label) {
var temperature;

output("Enter " + label + " temperature:");
temperature = input();

return temperature;
}

function calculateCelsius(fahrenheit) {
var celsius;

celsius = (fahrenheit - 32) * 5 / 9;

return celsius;
}

function calculateFahrenheit(celsius) {
var fahrenheit;

fahrenheit = celsius * 9 / 5 + 32;

return fahrenheit;
}

function displayResult(temperature, fromLabel, result, toLabel) {
output(temperature.toString() + "° " + fromLabel + " is " + result + "° " + toLabel);
}

function input(text) {
if (typeof window === 'object') {
return prompt(text)
}
else if (typeof console === 'object') {
var value = rls.question(text);
return value;
}
else {
output(text);
return line.trim();
}
}

function output(text) {
if (typeof document === 'object') {
document.write(text);
}
else if (typeof console === 'object') {
console.log(text);
}
else {
print(text);
}
}
```

## Try It

Copy and paste the code above into one of the following free online development environments or use your own JavaScript compiler / interpreter / IDE.