Typescript doesn't know what FormData is

Question

When trying to use window.FormData I get the following error:

The name 'FormData' does not exist in the current scope

The same happens to FileReader

It should, as there's an [issue](http://typescript.codeplex.com/workitem/720) about it, fixed already. What version of TypeScript is used? — raina77ow, May 31 '13 at 22:57
Weird. Ok, what if you use `FormData` without `window` prefix? — raina77ow, May 31 '13 at 23:06
Ah, so it does recognize FormData, but now how can I check if the browser supports it? Im using code that checks for window.FormData to search for browser support. — localhost, May 31 '13 at 23:10

score 14 · Answer 1 · answered Feb 20 '19 at 09:38

14

add dom to the lib array in the tsconfig.json of your project.

{
  "compilerOptions": {
    ...
    "lib": ["es2018", "dom"], // add `dom` to the array
    ...
  }
}

answered Feb 20 '19 at 09:38

score 1 · Answer 2 · edited Jun 02 '13 at 23:29

1

You can check a feature exists using:

if (window.FormData) {
    alert('Yes');
}

This relies on falsey checks - if you want to be explicit, use.

if (typeof FormData !== 'undefined') {
    alert('Yes');
}

edited Jun 02 '13 at 23:29

basarat

answered Jun 01 '13 at 08:27

Fenton

Falsey checks are bad for undefined since it throws an exception. Try it: http://jsfiddle.net/basarat/2MJ8j/ The explicit one is fine :) – basarat Jun 01 '13 at 23:11
I see that mate, but the falsey example is *wrong* "Undefined variables , like 'foo'. You'll get an error if you access an undefined variable in any context other than typeof." http://stackoverflow.com/a/2559513/390330 – basarat Jun 02 '13 at 23:26
1

you can use `if (window.FormData)` if you want the falsey check. `if (FormData)` is a straight up exception and not a functioning piece of code. Made the edit if thats okay :) – basarat Jun 02 '13 at 23:27

2 Answers2