create function with name

createFunction.js

function createFunc(name, args, fstr) {
  var arr = [name, args, fstr];
  var str = 'return function %s(%s) %s;';
  str = str.replace(/%s/g, function() {
    return arr.shift();
  });
  return new Function(str)();
}

var name = 'test';
var args = ['a', 'b'];
var fstr = '{ return a + b; }';
var func = createFunc(name, args, fstr);
console.log(func(1, 2));