Roku Inc. /zigman2/quotes/205087179/composite ROKU +1.23% announced Tuesday that it has agreed to purchase dataxu, a Boston-based advertising technology company, for $150 million in cash and stock. The dataxu platform gives marketers the ability to conduct bidding, place self-serve ads, and manage campaigns. Roku said in a release that the deal will give the company the ability to offer marketers one "data-driven software solution to plan, buy, and optimize their ad spend across TV and OTT providers." Shares were off 0.3% in midday trading Tuesday as the S&P 500 /zigman2/quotes/210599714/realtime SPX +0.50% was up 0.2%. Roku's stock has vastly outperformed the S&P 500 this year, rising 332% over 2019, compared with a 20% gain for the index.