Script below can be used in a HubSpot Contact Workflow to associate a contact to a company using the value stored in the "company name" property. If the company exists it is associated. If the company does not exist, it is created and associated. Requires authentication with a private app.

associateCompanyToContact.js

// Import the Hubspot NodeJS Client Library - this will allow us to use the HubSpot APIs
const hubspot = require('@hubspot/api-client');

//Instantiate a new HubSpot API client using an access token (private app)
const hubspotClient = new hubspot.Client({
    accessToken: process.env.HUBSPOTTOKEN
});

// Helper function to associate Company to Contact using HubSpot Client
function associateCompanyToContact(companyId, contactId) {
    const AssociationSpec = [{
        "associationCategory": "HUBSPOT_DEFINED",
        "associationTypeId": 2
    }];
    hubspotClient.apiRequest({
        method: 'PUT',
        path: `/crm/v4/objects/company/${companyId}/associations/contact/${contactId}`,
        body: AssociationSpec
    })
}

// Function called when custom coded worklow action executes
exports.main = (event) => {

    // Search for company using the contacts company name property
    const filter = {
        propertyName: 'name',
        operator: 'EQ',
        value: event.inputFields['company_name']
    }
    const filterGroup = {
        filters: [filter]
    }

    const properties = ['name']
    const publicObjectSearchRequest = {
        filterGroups: [filterGroup],
        properties,
    }

    hubspotClient.crm.companies.searchApi.doSearch(publicObjectSearchRequest).then(searchCompanyResponse => {
        if (searchCompanyResponse.total) { // If match found associate contact to company
            associateCompanyToContact(searchCompanyResponse.results[0].id, event.object.objectId);
        } else { // If no companies found create company and associate contact to company
            //Create a Company object
            const companyObj = {
                properties: {
                    name: event.inputFields['company_name'],
                }
            }
            hubspotClient.crm.companies.basicApi.create(companyObj).then(results => {
                associateCompanyToContact(results.id, event.object.objectId);
            });
        }
    });
}