Datatypes and variables
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Introduction to JavaScript |
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Data types
Though JavaScript is a weakly typed programming language, there are some 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 non-existent 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.