Uglifyjs: Way to reduce +=1 to ++ in for loops?

[jamessouth]

Bug report or feature request?

feature req

Uglify version (uglifyjs -V)

3.4.9

JavaScript input

for(var i = 0; i < 3; i += 1){
  console.log(i);
}

The uglifyjs CLI command executed or minify() options used.

uglifyjs [filename.js]

JavaScript output or error produced.

for(var i=0;i<3;i+=1){console.log(i)}

maybe this is a source code issue and outside the scope of minification, just wondering if there was/could be an option to turn +=1 and -=1 to ++ and -- ?

[fabiosantoscode]

Added the feature to terser, under the existing "loops" option.

[fabiosantoscode]

Released as terser 3.10.8

[fabiosantoscode]

You might want to pin that version, as I had to revert the feature due to issues. I might try to do it again sometime, but for now it's out.

[Skalman]

It's very tricky to do correctly, because when the variable is a string it change the meaning:

// 0, 1, 2
for(var i = 0; i < 3; i += 1){console.log(i)}

// "0", "01"
for(var i = "0"; i < 3; i += 1){console.log(i)} //

[drathier]

Maybe an "assume no implicit type coercion anywhere" optimization flag could be useful?

[Skalman]

@drathier, you'd have to specify it much more clearly than that. E.g. I agree that "hello" + 123 is implicit, but "" + 123 is an explicit conversion - that's the easiest way to convert a number to a string.

[drathier]

"hello" + 123 is just as explicit as "" + 123. What I meant was that n + 123 could assume that n is a number