autolib javascript

this is the javascript version of the auto library.

basic idea

the simplest example looks like this:

let auto = require('@autolib/auto');

let _ = auto({
    x: 10,
    y: _ => _.x * 2,
    log: _ => console.log('y =',_.y)
})

when you run this you should see

$ node test.js
y = 20

the variable we get back (in this case _) has accessors attached to it so you can

// add this after let _ = auto({ ... })
_.x = 5

at which point both y and log will get triggered, i.e.

$ node test.js
y = 20
y = 10

separate objects

you can have several object that refer to one another.

let { cache, error, pubsub } = require('@autolib/default');

let auto = obj => require('@autolib/auto')(obj, { cache, error, pubsub });

let a = auto({
    x: 10,
    y: _ => _.x * 2 + _.w,
    log: _ => console.log('y =',_.y) // this will run any time y changes
});

let b = auto({
    w: 2,
    z: _ => _.x + _.y,
    log: _ => console.log('z =',_.z) // this will also run but when z changes
});

a.x = 5;
b.w = 3;

each auto object uses a cache for storing values, an error object for reporting on exceptions and a pubsub for connecting with a publish / subscribe mechanism

above we get default objects for each of these (you can also use your own custom objects, or wrap the defaults - see below) and use them all to create a and b, which each refer to values the other defines.

custom core objects

you can easily pass in your own versions of the core objects, for example if you wish to use a database for the cache store, want to send any errors to a server, or if you want to connect auto objects over a transport (auto objects are separable, see above).

all you need do is create a function which returns the correct function names. see cache.js, error.js and pubsub.js in the source for examples (they are quite simple).

alternatively you could just wrap the core functionality using the prehook (or posthook) function e.g.

let evts = [];
let log = (obj,v,fn,parm) => parm ? evts.push({ obj,v,fn,parm }) : evts.push({ obj,v,fn });

let { cache } = require('@autolib/prehook')(log);
let auto = require('@autolib/auto');

auto({
    x: 10,
    y: _ => _.x * 2
})

console.log('evts',evts);

this will print out a log of everything that has occured in the cache:

$ node test.js
evts [
  { obj: 'cache', v: 'x', fn: 'set', parm: 10 },
  { obj: 'cache', v: 'y', fn: 'has', parm: 'x' },
  { obj: 'cache', v: 'y', fn: 'get', parm: 'x' },
  { obj: 'cache', v: 'y', fn: 'set', parm: 20 }
]