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Writing self-executing functions with !function(){}() is sometimes unsafe #625
Description
Consider the example:
(function(){ doSideEffects(); return 5; })() // A
versus
!function(){ doSideEffects(); return 5; }() // B
A and B cause the same side effects, but the result of each expression is different, 5 in A and false in B
I am uglifying code files that look something like A, which are rewritten to B, and I am running into this issue because the minified files are passed to a processor that uses the result of eval() on the minified code.
I did not find a flag to uglify that controls this behavior, but I was curious whether:
- Such a flag exists
- There is a way around this problem without hacking around uglify
- There should be a flag (or patch) for this
- Other thoughts of people who understand Uglify better than I do
Activity
mishoo commentedon Jan 27, 2015
There is a flag, try passing
-c negate_iife=false.michaelficarra commentedon Jan 28, 2015
That is not the right answer. You are looking to preserve the program completion value. See #543 for the previous discussion about this.
mpcref commentedon Jan 30, 2015
I propose the following fix:
never negate an IIFR that is also the program completion value.
New issue #628 created.
rvanvelzen commentedon Feb 11, 2015
Track #640 for follow-up.
process code with implicit return statement
process code with implicit return statement
process code with implicit return statement
process code with implicit return statement (#1522)