jQuery is a library that is currently used for faster and easier DOM manipulation. It allows you to download, move, delete, animate items, assign Event Listeners (such as clicking), iterate between items and much more. Based on it, many smaller or larger libraries were created, such as Owl Carousel which is used to create advanced sliders, or Jquery UI which is used to quickly create user interface elements such as fields with auto-completion or progress bars. It was created by default to facilitate the integration of code between individual browsers. These days such integration is carried out using transpilers like Babel, and the browsers have become more consistent.

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