Online advertising firm Conversant Inc. agreed on Thursday to be acquired for $2.3 billion in cash and stock. The Westlake Village company formerly known as ValueClick will be acquired by Alliance Data Systems Corp., a data marketing service provider. “Gaining access to the huge data-driven platforms at Alliance Data will allow the combined entity to offer clients an end-to-end solution across all channels,” said John Giuliani, Conversant’s chief executive, in a statement. Alliance Data, in Plano, Texas, offers data-driven marketing services for managing customer loyalty programs for retailers. Conversant specializes in affiliate marketing programs and will become a subsidiary of Alliance. ValueClick pioneered the pay-per-click model of Internet ads, in which an advertiser only pays when an Internet visitor clicks on the ad. In recent years, the company has moved aggressively into affiliate marketing, in which websites advertising a product receive a percentage of revenue if visitors from their site buy the product. Conversant conducts much of its business through its subsidiary CJ Affiliate, formerly known as Commission Junction. Conversant shares jumped 30 percent Friday, closing up $8.09 to $34.80 on the Nasdaq.