When it is needed to display dynamic content, template engines are used. They work pretty simple: to the existing template a specific set of data is applied and some of dataset representation is obtained. If data is changed, it has to be displayed in a representation. A programmer needs to write the code which alters representation and synchronizes data changes in one. But, if we already have a template, why don’t we use it? The idea to use template not just at initial rendering but after every data change is fundamental in React JS.
However, for displaying data changes, programmers have to manipulate DOM tree and write code which displays all updates in different specific cases. React JS library is aimed at solving this problem.