The most popularly known framework that is being used by various big companies is React which was built by Facebook. The company originally built this because Facebook Ads were increasing and growing faster everyday, and the job of handling them was becoming extremely difficult. To simplify their works, they built a library to make their work easier but later they released it to the public and made it open-source.
Another popular open-source framework is Ember.js that was released originally by Yehuda Katz, and many other companies support the framework which uses Ember.js such as LinkedIn and Yahoo.
Many large companies use it such as Apple Music was built using Ember as the framework is highly scalable and is suitable for larger scale projects. Ember comes with various built in tools which are easier to get started with and even for working with backend data, it provides data and is highly flexible and convention over configuration is preferred by it. This framework has been in the market for over 10 years and is getting better day by day, and definitely the best one to learn.