jetfun

Convert JSON expressions to functions

This node.js package is used to convert a JavaScript object into a function. Although this package supports a wide variety of use-cases, it was originally intended to allow a browser to send a complex operation to a web server as a single JSON expression.

jetfun(expression) → function

Below is a simple example of converting a greeting object into a function. Once converted, the object can be bound to, or called against, any Object exposing the desired methods.

var jetfun = require('jetfun');

function English() { }

// greet someone in English
English.prototype.greet = function(e) {
  if (e.sex === 'male') {
    console.log('Hello Mr. ' + e.greet);
  }
  else {
    console.log('Hello Mrs. ' + e.greet);
  }
};

function Spanish() { }

// greet someone in Spanish
Spanish.prototype.greet = function(e) {
  if (e.sex === 'male') {
    console.log('Hola Señor ' + e.greet);
  }
  else {
    console.log('Hola Señora ' + e.greet);
  }
};

// convert the JSON expression to a function
var greetChris = jetfun({
  greet: 'Chris',
  sex: 'male'
});

greetChris.call(new English());
// => Hello Mr. Chris

greetChris.call(new Spanish());
// => Hola Señor Chris

handler(expression, value, [callback])

The handler function that is invoked must take the expression as the first argument. If the length property of the handler function is greater than two, then the callback must be called; otherwise, the function resolves to the return value of the handler function. The return value is assumed to be a promise if it has a then method.

Below is an example demonstrating each form of handler function and how they operate.

var jetfun = require('jetfun'),
    when = require('when');

function Calculator() { }

Calculator.prototype.clear = function() {
  return 0; // return a value
};

Calculator.prototype.add = function(e, value, callback) {
  callback(null, value + e.add); // callback with a value
};

Calculator.prototype.substract = function(e, value) {
  return when(value - e.substract); // return a promise
};

var fun = jetfun({
  do: [
    { clear: null },
    { add: 3 },
    { subtract: 1 }
  ]
});

fun.call(new Calculator(), function(err, value) {
  console.log(value); // => 2
});