CODEWITHSUNDEEP
typescriptform-data
N.Bar
N.Bar

Reputation: 135

Why is my FormData object always empty?

I'm trying to add some data to formData like this:

params = {'code': 'h1'}
const formData: FormData = new FormData();
formData.append('parameters', JSON.stringify(params));

When I try to get the data from the formData like this: formData['parameters'] it returns undefined and formData.entries.length is 0. I looked at some sites and saw that this is the way to do that. What am I doing wrong?

Thanks.

Upvotes: 10

Views: 15907

Answers (2)

Daniel Beck
Daniel Beck

Reputation: 21485

You're declaring the formData object incorrectly (edit: for javascript. The question wasn't originally tagged with typescript, which I'm not familiar enough with)

const params={'code': 'h1'}
const formData = new FormData()
formData.append('parameters', JSON.stringify(params))
// confirm:
console.log(formData.get('parameters'))

...but in case you're trying to set multiple parameters on formData, instead of just one named "parameters", you might want to be doing this instead:

const params={
  'code': 'h1',
  'foo': 'bar'
}

const formData = new FormData()
Object.keys(params).forEach((k) => {
  formData.append(k, params[k])
})

// confirm:
console.log(formData.get('code'))
console.log(formData.get('foo'))

Upvotes: 2

Krisztián Balla
Krisztián Balla

Reputation: 20361

Your FormData object is actually not empty. The way you are trying to access the data after appending it, is wrong.

For me the following works:

const params = {'code': 'h1'}
const formData = new FormData();
formData.append('parameters', JSON.stringify(params));

for (const entry of formData.entries())
{
    document.write(entry);
}

Side notes:

  • As formData.entries() returns an interator object, there is no length property.
  • There is also no indexer [] defined. So you need to retrieve values using the get() method as shown by Daniel Beck in his answer.

Upvotes: 9

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