PHP has different functions which can be used to test the value of a variable. Three useful functions for this are isset(), empty() and is_null(). Like most computer languages, JavaScript supports Boolean data types; values which can be set to true or false. In addition, everything in JavaScript has an inherent. Revision 2.93 Aaron Whyte Bob Jervis Dan Pupius Erik Arvidsson Fritz Schneider Robby Walker This style guide contains many details that are initially hidden from. JavaScript does not feature a classical inheritance model; instead, it uses a prototypal one. While this is often considered to be one of JavaScript's weaknesses, the. Well organized and easy to understand Web bulding tutorials with lots of examples of how to use HTML, CSS, JavaScript, SQL, PHP, and XML. JavaScript Tutorial. Introduction; Embedding JavaScript into an HTML Document; Variables. What are Variables? Values of Variables; Data Type Conversion. Literals var x; // defines the variable x and assigns to it the special value undefined (not to be confused with an undefined value) var y = 2; // defines the variable y and. I have a text box element whose value I am trying to access using document.getElementById( id-name ).value. I find that the call is returning a null instead of empty. We’re not particularly doing anything useful with foo here, but notice that the script fails out anyway. At this point any code that follows will not be executed. I saw this thread, but I didn't see a JavaScript specific example. Is there a simple string.Empty available in JavaScript, or is it just a case of checking for ?.