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Lesson Understanding Uninitialized Variables

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Rafael J. Rodriguez edited this page Jan 6, 2017 · 2 revisions

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Understanding Uninitialized Variables

When JavaScript variables are declared, they have an initial value of undefined. If you do a mathematical operation on an undefined variable your result will be NaN which means "Not a Number". If you concatenate a string with an undefined variable, you will get a literal string of "undefined".

Basically this means that before you do any operations with them you must assign an initial value at some point.

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