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e4x Interview Questions with Answers
Introduction of E4X

E4X means "ECMAScript For XML". It is a standard extension to ECMAScript. So in real life E4X means "JavaScript for XML". ECME (The European Computer Manufacturers Association) is the organization standardizing JavaScript. ECMAScript is the official name for JavaScript. ECMAScript is the same as JavaScript. ECMAScript for XML (E4X) is a programming language extension that adds native XML support to JavaScript. It does this by providing access to the XML document in a form that feels natural for ECMAScript programmers. The goal is to provide an alternative, simpler syntax for accessing XML documents than via DOM interfaces.

History of E4X-

  • ECMA-262 (JavaScript 1.3) was standardized in December 1999.
  • E4X is an extension of JavaScript that adds direct support for XML.
  • ECMA-357 (E4X) was standardized in June 2004.
  • E4X is standardized by ECME International in ECMA-357 standard (currently in its second edition, December 2005).
  • E4X is implemented (at least partially) in SpiderMonkey (Gecko's JavaScript engine) and in Rhino (JavaScript engine written in Java).

Advantage of E4X

  • Improve performance and maintainability.
  • Decrease coupling between code and external data (in form of XML).
  • Reduce code complexity, time to market, and revision cycles.
  • Simplify the ability of Web developers to use the power of XML by using their existing skills and knowledge, and reusing familiar concepts, operators, and syntax (i.e., E4X makes XML very simple to use.)
  • ntegrate well with other languages designed for manipulating XML, such as XPath, XSLT, and XQuery (For example, E4X should be able to invoke complementary languages when additional expressive power is needed without compromising the simplicity of the E4X language itself.)
  • Standardize the syntax and semantics of a general-purpose, cross-platform, vendor-neutral set of programming language extensions by adding native XML support in ECMAScript.

Disadvantage of E4X

  • It is not currently possible to access a DOM object through E4X.
  • E4X doesn't support parsing XML declaration .