How to execute a Javascript function only after multiple other functions have completed?

Question

My specific problem is that I need to execute a (potentially) large number of Javascript functions to prepare something like a batch file (each function call adds some infor

Answer 1

I was looking for the same kind of pattern. I am using APIs that interrogate multiple remote data sources. The APIs each require that I pass a callback function to them. This means that I cannot just fire off a set of my own functions and wait for them to return. Instead I need a solution that works with a set of callbacks that might be called in any order depending on how responsive the different data sources are.

I came up with the following solution. JS is way down the list of languages that I am most familiar with, so this may not be a very JS idiom.

function getCallbackCreator( number_of_data_callbacks, final_callback ) {

    var all_data = {}

    return function ( data_key ) {

        return function( data_value ) {
            all_data[data_key] = data_value;

            if ( Object.keys(all_data).length == number_of_data_callbacks ) {
                final_callback( all_data );
            }
        }
    }
}

var getCallback = getCallbackCreator( 2, inflatePage );

myGoogleDataFetcher( getCallback( 'google' ) );
myCartoDataFetcher( getCallback( 'cartodb' ) );

Edit: The question was tagged with node.js but the OP said, "I'm looking for a general Javascript programming pattern for this," so I have posted this even though I am not using node.