Question

var myString = '';
myString += 'foo';
myString += 'bar';
myString = myString.replace(/oba/, 'qux');

console.log(myString) // produces "foquxr"

Is there any way to likewise tinker around with functions, like, say, turning function(a) { a += 'b'; return a; } info function(a) { a += 'b'; console.log(a); return a + 'c'; }?

Answer 1

You can compose functions thus

// (compose(f, g))(x, y, ...) is the same as f(g(x, y, ...)) 
function compose(f, g) {
  return function (var_args) {
    return f.call(this, g.apply(this, arguments));
  };
}

so

var f = compose(
  function (x) { console.log(x); return x + 'c'; },
  function (a) { a += 'b'; return a; });

lets you combine two small functions to get a function that behaves like

function(a) { a += 'b'; console.log(a); return a + 'c'; }