A most simple promise system, to explain promises

basic-promise.js

// A most simple promise system, to explain promises

var p = promise( function ( resolve, reject ) {
    // do async stuff here
    fs.readFile( function ( err, file ) {
        if ( err ) {
            reject( new Error( 'it mucked up' ) );
        } else {
            resolve( file );
        }
    });

});

p.success( function ( value )  {
    console.log( 'I got the value', v );
});

p.error( function ( err ) {
    console.log( 'It failed', err );
    throw err;
});


function promise ( fn ) {
    var onSuccess = function () {};
    var onError = function () {};

    setTimeout( function () {
        fn( function () {
            onSuccess.apply( this, arguments );
        }, function () {
            onError.apply( this, arguments );
        });
    }, 0 );

    return {
        success: function ( fn ) { onSuccess = fn; },
        error: function ( fn ) { onError = fn; }
    };
}