Rule suggestion: Avoid modifying object references

In my opinion it is generally dangerous to change the input parameter of a function if it is not a primitive type. It could e.g. result in side effects that are hard to debug because the referenced object is changed in the function.

While I think we won’t be able to detect every possible fault, I suggest creating a rule that at least catches the simple case:

// These cases could be an error or a warning if the rule is enabled
function foo1 (bar) {
    bar.thisPropertyAlreadyExisted = somethingElse;
}

function foo2 (bar) {
    delete bar.thisPropertyAlreadyExisted;
}

// This is most likely to hard to implement
function foo3 (bar) {
    var temp = bar.thisPropertyAlreadyExisted;
    temp.deepProperty = somethingElse;
}

What do you think about this?

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[feross]

Is there any way to get the { props: true } behavior without enabling no-param-reassign?

[nzakas]

I’d say don’t worry about anything that needs path analysis. Just doing a basic check is good enough to start.