Custom contact field object key

[nodesocket]

I have a custom field for contacts defined as:

Howerver, what is the object key in JavaScript when creating a contact? I've tried:

var contact = {};
contact.plan = 'Unsure'; // does not work
contact.plan_interest = 'Unsure'; // does not work
contact.planInterest = 'Unsure'; // does not work

[MattCode-dev]

this works:

contact['Plan interest'] = 'test';