I have a JSON file, I'm trying to change a particular value in it using a script.

"foo-bar": "baz",

It is set as baz in this example, but in practice I don't know what this value is.

I want to change foo-bar's value from within a larger script.

"foo-bar": "qux",

I tried

$var='qux'
jq --arg passvar ${var} '{"foo-bar":$passvar}' file.json

I get the correct output in terminal

{
"foo-bar": "qux"
}

But when I check the actual file contents using vim, I get

"foo-bar": "baz",

jq doesn't want to save the new file.json? Or is that a preview of some sort? What am I missing? Is there a better way than jq to update/set values in a json file?

*edited to add a dash to the initial variable, it is now foo-bar instead of just foo.