Detect if JavaScript object is a FormData instance

Question

I was looking for a way to check if an object is a FormData instance, similarly to Array.isArray()

Edit: If someone knows about instanceof, they obviously won't need to be pointed to instanceof. Obviously not a duplicate.

Possible duplicate of [What is the instanceof operator in JavaScript?](https://stackoverflow.com/questions/2449254/what-is-the-instanceof-operator-in-javascript) — hackerrdave, Sep 11 '17 at 00:05
@hackerrdave how to detect if a JavaScript object is an instance of FormData — km6, Sep 11 '17 at 00:05
@km6—then perhaps that question should be in the text of your question somewhere. — RobG, Sep 11 '17 at 00:55

score 45 · Accepted Answer · answered Sep 11 '17 at 00:02

45

Use instanceof

For example:

let formData = new FormData()
let time = new Date()

console.log("statement: formData is a FormData instance", formData instanceof FormData) // statement is true
console.log("statement: time is a FormData instance", time instanceof FormData) // statment is false

Source

answered Sep 11 '17 at 00:02

km6

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The reason there's an *isArray* mehtod is that *instanceof* does not work across frames (or global environments) where the constructor is in one environment but the object was created in the other. You seem to have dismissed *instanceof* in your OP, then post an answer using it. What's the point? – RobG Sep 11 '17 at 00:58

Detect if JavaScript object is a FormData instance

1 Answers1