Adds lists to an object, pushing to a list if a known key is specified.

popArray.js

// works well with querystring.stringify to produce GET parameters

function objectArrayPush(data, key, value) {
    if (typeof data[key] != 'undefined' && data[key] instanceof Array) {
        // EXISTS: pushing onto list
        data[key].push(value);
    } else {
        // CREATING: pushing onto list
        data[key] = [];
        data[key].push(value);
    }
    return data;
}

var data = {};

console.log(objectArrayPush(data, 'foo', 'bar'));
console.log(objectArrayPush(data, 'foo', 'baz'));
console.log(objectArrayPush(data, 'bob', 'blip'));
console.log(objectArrayPush(data, 'foo', 'womp'));

/*
Output:
{ foo: [ 'bar' ] }
{ foo: [ 'bar', 'baz' ] }
{ foo: [ 'bar', 'baz' ], bob: [ 'blip' ] }
{ foo: [ 'bar', 'baz', 'womp' ], bob: [ 'blip' ] }
*/