CODEWITHSUNDEEP
javascript
Nurbol Alpysbayev
Nurbol Alpysbayev

Reputation: 21891

What is the full list of ways to modify a primitive?

I am writing some syntactical analyzer that disallows changing a primitive.

So I know that one can modify primitives these ways:

let p // a primitive

p = 1
p += 1
p -= 1
p %= 1
p *= 1

Is it really a full, exhaustive list of ways to change a primitive? Or did I forget something...

P.S. The analyzer is for my peculiar library. It disallows to change a passed argument to a function that returns an object literal of test closures, i.e. each closure must not change their common primitive.

Upvotes: 1

Views: 68

Answers (1)

Jonas Wilms
Jonas Wilms

Reputation: 138307

Here you go:

 // assignment operators
 p = 1; 
 p += 1;
 p -= 1;
 p *= 1;
 p /= 1;
 p %= 1;
 p <<= 1;
 p >>= 1;
 p >>>= 1;
 p &= 1; 
 p ^= 1;
 p |= 1;
 p **= 1;
 // decrement / increment operators
 p++;
 ++p;
 p--;
 --p;
// destructuring
({ p } = { p: 1 });
({ a: p } = { a: 1 });
([p] = [1]);

Note that all of the above could also occur in a parsed string:

 (new Function("p = 1"))();
 eval("p = 1");

The analyzer is for my peculiar library. It disallows to change a passed argument.

Then I guess the easiest is to just parse:

 function toTest(p) { /* body */ }

to this and execute it:

 const p = 1;
 try {
   eval(/* body */);
} catch(e) {
  //...
}

If an error occurs, someone tried to mutate the const.

Upvotes: 1

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