How to inline function calls in JavaScript?

Question

I need a function expand(fn), that will accept any function and return a function where all the function calls in the input function are replaced with codes of these functions.

For example, given f and g functions below:

function f(x) {
    console.log('f: ' + x);
}

function g(x) {
    console.log('g: ' + x);
    f(x + 1);
}

expand(g) should return such a function:

function anon(x) {
    console.log('g: ' + x);
    var arg1 = x + 1;
    {
        console.log('f: ' + arg1);
    }
}

expand(g) should work just as the function g. But expand(g) should not call any functions except standard JavaScript functions.

Such an expand function would be handy when I'm going to pass just a plain JavaScript function to a foreign sandbox and I want to be able to use my functions and other JS libraries in that function to be executed there.

I'd like to be able to expand functions with parameters, functions from external libraries and nested functions. Even recursive functions could be converted to loops but I'm not looking for that for now.

What's the difference between `anon` and `g`? Couldn't `expand(fn)` just return `fn`? — recursive, May 24 '16 at 23:36
@recursive `f()` in `g` is replaced with the body block of `f`. — Han Tuzun, May 24 '16 at 23:38
@2426021684 I want to expand function calls inside a body with their respective bodies recursively. But I also want to pass the function parameters inside these bodies. — Han Tuzun, May 24 '16 at 23:40
That sounds like you want to modify source code at runtime. That's not really possible, unless you want to use a JS parser, to some AST transformation, print the AST and `eval` the result. — Felix Kling, May 24 '16 at 23:40
@EmrehanTuzun why would want to do this? anon does the same thing as g — michaelmesser, May 24 '16 at 23:40
Related: https://stackoverflow.com/questions/6009411/tool-to-automatically-inline-javascript-function-calls — michaelmesser, May 24 '16 at 23:41
@FelixKling I'm willing to start such an open source project :) — Han Tuzun, May 24 '16 at 23:46
@2426021684 Because I'm going to pass this function to a foreign sandbox and I want to be able to define functions and use JS libraries in my function to be executed there. — Han Tuzun, May 24 '16 at 23:48
Well, it already exists ;) (kind of) https://babeljs.io/ But usually this is done as a compile step, not at runtime. This will also easily break if `f` in your example was a closure. — Felix Kling, May 24 '16 at 23:48
@EmrehanTuzun easier to include the library in the foreign sandbox — michaelmesser, May 24 '16 at 23:50
@EmrehanTuzun: What should `expand()` do if it contains a call to a function which uses a variable from an enclosing scope? That can't be inlined. — recursive, May 24 '16 at 23:51
@2426021684 it's not possible to include libraries in Postman sandboxes, and many others. — Han Tuzun, May 24 '16 at 23:52
@recursive it can pass the variable in the head of the expanded function block. If it's not available at runtime it can just throw an error. — Han Tuzun, May 24 '16 at 23:54
Or maybe you want something like: http://sweetjs.org/ ... (also a compile step) — bazeblackwood, May 24 '16 at 23:56
@FelixKling that makes sense. Do you know where can I start? — Han Tuzun, May 24 '16 at 23:57
@pizzasynthesis, sweet.js looks, well, sweet! Have you ever written plugins for sweet or babel? — Han Tuzun, May 24 '16 at 23:58

How to inline function calls in JavaScript?

0 Answers0