Adding values to FormData - javascript

Question

let formData = new FormData();
 formData.append('File', document.file);
 formData.append('DocumentType', document.documentType);
 product = {
 ...values,
 productType: productT,
 };
 for (var key in product) {
 if (key != 'createdDate' && key != 'expirationDate') {
 formData.append(key, product[key]);
 } else {
 formData.append(key, new Date(product[key]).toUTCString());
 }
 }
 await createproduct(formData);

I need to send file and other data about product in one request so I added all the stuffs in FormData, and I have issues only with Dates, I must convert it to date because somehow it get confused if I don't convert it.

Can I somehow refactor this code to do this part about dates more elegant, if condition in for loop somehow smells bad..

P.S EDIT:

for (var key in product) {
 const transform = DateTransformer[key];
 formData.append(key, transform ? transform[product[key]] : product[key]);
}

Answer 1

Transformation rules

Especially useful if there are many fields and each needs a unique rule.

const dateToUTCString = d => new Date(d).toUTCString();
const DataTransformer = {
 createdDate: dateToUTCString,
 expirationDate: dateToUTCString,
};
// [...]
for (const [key, calue] of Object.entries(product)) {
 const transform = DataTransformer[key];
 formData.append(key, transform ? transform(value) : value);
}

• Roxy'Pro: I don't understand how this works..
• woxxom: The code is a standard JavaScript so I'm not sure what to clarify.