Is “use strict” Safe for Live Sites?

Question

\"use strict\"; seems awesome, and we\'d really like to use it at our shop. However, we just want it so that we (the developers) can find strictness-issues; we very much DO

Answer 1

It's the latter. While beeing in strict mode, an Javascript interpreter may throw error messages at runtime, which would not get thrown in non-strict mode.

On the other hand, most of these errors are "good errors", which means, they will actually help not breaking your code.

For instance

function foo() {
    "use strict";
    bar = true;
}

foo();

This will throw

"ReferenceError: assignment to undeclared variable bar"

in strict mode, which is a good thing. In non strict mode, we would just have created a global variable called bar, which is probably not what we wanted. There are plenty of other situations where strict mode prevents the programmer from doing something stupid/bad/unwanted and throws error messages. But again, you want to have those errors instead of some wierd bugs.

Have a further read on MDN