Is there any fast tool which performs constant sub

Question

For example, setting MYCONST = true would lead to the transformation of

 if (MYCONST) {
     console.log('MYCONST IS TRUE!'); // print important message
 }

to

 if (true) {
     console.log('MYCONST IS TRUE!'); // print important message
 }

This tool ideally has a fast node.js accessible API.

Answer 1

Edit: Whoops. Gotta read title first. Ignore me.

Google Closure Compiler has such a feature:

You can combine the @define tag in your code with the --define parameter to change variables at "compile" time.

The closure compiler will also remove your if-statement, which is probably what you want.

Simply write your code like this:

/** @define {boolean} */
var MYCONST = false; // default value is necessary here

if (MYCONST) {
    console.log('MYCONST IS TRUE!'); // print important message
}

And call the compiler with the parameter:

java -jar closure-compiler.jar --define=MYCONST=true --js pathto/file.js

Regarding you API request: Closure Compiler has a JSON API.

Answer 2

The Apache Ant build system supports a replace task that could be used to achieve this.

Answer 3

Patch a beautifier, for example

• Get the JS Beautifier https://raw.github.com/einars/js-beautify/master/beautify.js written in JS.

• Replace the last line of function print_token() by something like

  output.push(token_text=="MYCONST"?"true":token_text);

• Call js_beautify(your_code) from within nodejs.

Answer 4

google's closure compiler does, among other things, inlining of constants when annotated as such, leaving string content untouched but I am not sure if it's a viable option for you.

Answer 5

A better way to achieve what you want -

Settings.js

 settings = {
   MYCONST = true
 };

MainCode.js

 if (settings.MYCONST) {
     console.log('MYCONST IS TRUE!'); // print important message
 }

This way, you make a change to one single file.