Chapter 1: Exploring the Core Concepts of JavaScript

The JavaScript language was created (in the mid-1990s) to be executed in internet browsers, in order to make websites more fluid. It was originally used to control what was entered into input forms. For example, it was used to do the following:

  • Allow the entry of numeric characters in a field – and only numeric ones. Other characters, for example, letters, had to be rejected in this case. This made it possible, thanks to the JavaScript language included in the browser, not to validate the entry of the form and avoid sending data to the server, which would have indicated an entry error in this case.
  • Check that the mandatory fields of the form were all entered, by checking all the fields ...

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