How to add key-value to object in JS? [closed]

Question

I found this expression, but I do not know where is it come from? Where is any documentation for it?

onChange={(
    event: React.ChangeEvent<HTMLInputElement>
) => {
    setFormData({ ...formData, [key]: event.target.value })
}}

Answer 1

You can just put any key name here i chose eventValue

setFormData({..formData, eventValue: event.target.value})

and then you should be able to access it like this

function setFormData(formDataObject){
    // access it like this
    formDataObject.eventValue
}