Difference between revisions of "Datatypes and variables"
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* '''boolean''': A variable of type boolean may hold the special values ''true'' or ''false''. If a number value is used where a boolean expression is expected, a zero value will be treated like ''false'' and any other value will be treated as ''true''.  * '''boolean''': A variable of type boolean may hold the special values ''true'' or ''false''. If a number value is used where a boolean expression is expected, a zero value will be treated like ''false'' and any other value will be treated as ''true''.  
* '''number''': This type is a set of values representing integer and floating point numbers. In ECMAScript, the set of values represents the doubleprecision [http://en.wikipedia.org/wiki/IEEE_754 64bit format IEEE 754] values including the special values ''NotaNumber'' (NaN), ''positive infinity'' (Infinity), and ''negative infinity'' (Infinity).  * '''number''': This type is a set of values representing integer and floating point numbers. In ECMAScript, the set of values represents the doubleprecision [http://en.wikipedia.org/wiki/IEEE_754 64bit format IEEE 754] values including the special values ''NotaNumber'' (NaN), ''positive infinity'' (Infinity), and ''negative infinity'' (Infinity).  
−  * '''string''': A variable of type string is  formally spoken  a finite ordered sequence of at least zero 16bit unsigned integer values. Practically it is just a string, like you may know from C++ or Java. In C it's like character array, but with 16 bit characters instead of 8 bit Cchar. Single characters of a string can be accessed just like in any other major Clike programming language using square brackets.  +  * '''string''': A variable of type string is  formally spoken  a finite ordered sequence of at least zero 16bit unsigned integer values. Practically it is just a string, like you may know from C++ or Java. In C it's like a character array, but with 16 bit characters instead of 8 bit Cchar. Single characters of a string can be accessed just like in any other major Clike programming language using square brackets. The first character has index 0. 
Revision as of 07:25, 16 July 2009
Introduction to JavaScript 


Data types
Though JavaScript is a weakly typed programming language, there are some primitive data types between which JavaScript sometimes variables automatically converts:
 null: Null means variable has no value at all. Do not confuse null with 0 (zero)! 0 is just a number, null means just no value or a empty or nonexistent reference.
 undefined: A value that is undefined is a value held by a variable right after it has been created and before a value has been assigned to it.
 boolean: A variable of type boolean may hold the special values true or false. If a number value is used where a boolean expression is expected, a zero value will be treated like false and any other value will be treated as true.
 number: This type is a set of values representing integer and floating point numbers. In ECMAScript, the set of values represents the doubleprecision 64bit format IEEE 754 values including the special values NotaNumber (NaN), positive infinity (Infinity), and negative infinity (Infinity).
 string: A variable of type string is  formally spoken  a finite ordered sequence of at least zero 16bit unsigned integer values. Practically it is just a string, like you may know from C++ or Java. In C it's like a character array, but with 16 bit characters instead of 8 bit Cchar. Single characters of a string can be accessed just like in any other major Clike programming language using square brackets. The first character has index 0.