Currency Conversion Function

[Sam Moffatt]

Every so often I buy something that isn’t directly in USD and want to have a quick way of converting it back to USD. I ended up using a free currency converter API which requires a simple registration to get an API key (replace the string PUT_YOUR_API_KEY_HERE with the API key they assign you). Apart from that it has a reasonably generous amount of requests (100 an hour).

Here’s the script, intended to be saved as a form script named ‘Currency Converter’ in a form named ‘Script Manager’ similar to the logger module:

// ========== convertCurrency Start ========== //
// NAME: Convert Currency
// VERSION: 1.1
// CHANGES:
//  1.1: Add options for different API, update to v7.

document.getFormNamed('Script Manager').runScriptNamed('Logger');

/**
 * Convert from one currency to another using a free web serive.
 *
 * source_currency: 		The source currency to convert from (e.g. CAD).
 * destination_currency:	The destination currency to convert into (e.g. USD).
 * amount:					The amount in the source currency to convert into destination currency.
 *
 * return: float value of converted currecny or false on error.
 */
function convertCurrency(source_currency, destination_currency, amount)
{
	var services = { "free" : "https://free.currconv.com", 
						"prepaid": "https://prepaid.currconv.com",
						"premium": "https://api.currconv.com"
					};
					
	var apiKey = 'PUT_YOUR_API_KEY_HERE';
	var currency_key = source_currency + "_" + destination_currency;
	var url = `${services['free']}/api/v7/convert?compact=ultra&apiKey=${apiKey}&q=${currency_key}`;
	
	logger.logMessage(`Requesting from URL: ${url}`);

	// Make the request.
	var forex = Utils.getJsonFromUrl(url);
			
	// Check the response matches.
	if (forex && forex[currency_key])
	{
		logger.logMessage(`Conversion for ${source_currency} to ${destination_currency} is ${forex[currency_key]}`);
		return forex[currency_key] * amount;
	}
	else
	{
		logger.logMessage("Unknown response received from URL: " + JSON.stringify(forex));
		return false;
	}
}
// ========== convertCurrency End ========== //

That one is simple: put in the currency you start with and the currency you want to land in and the amount. The API could do the amount calculation itself but I find it interesting to see what the raw value is and handle the multiplication in my own code.

In my case this is then connected to a field script that looks at a total field and a currency field to populate a USD total field. It’s a little more complicated because I do some math to get the total (shipping fee, taxes and total cost).

Simple example:

document.getFormNamed('Script Manager').runScriptNamed('Currency Converter');
convertCurrency('CAD', 'USD', '123.45');

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