3Language Basics


  • Reviewing syntax
  • Working with data types
  • Working with flow-control statements
  • Understanding functions


Please note that all the code examples for this chapter are available as a part of this chapter's code download on the book's website at www.wrox.com/go/projavascript4e on the Download Code tab.

At the core of any language is a description of how it should work at the most basic level. This description typically defines syntax, operators, data types, and built-in functionality upon which complex solutions can be built. As previously mentioned, ECMA-262 defines all of this information for JavaScript in the form of a pseudolanguage called ECMAScript.

ECMAScript as defined in ECMA-262, fifth edition, is the most-implemented version among web browsers. The sixth edition is the next to be implemented in browsers, and as of the end of 2017, most major browsers have mostly or fully implemented the specification. For this reason, the following information is based primarily on ECMAScript as defined in the sixth edition.


ECMAScript's syntax borrows heavily from C and other C-like languages such as Java and Perl. Developers familiar with such languages should have an easy time picking up the somewhat looser syntax of ECMAScript.


The first concept to understand is that everything is case-sensitive; variables, function names, and operators are all case-sensitive, meaning that ...

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