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Challenge Understanding Uninitialized Variables
Quincy Larson edited this page Aug 20, 2016
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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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JS Concepts
JS Language Reference
- arguments
- Array.prototype.filter
- Array.prototype.indexOf
- Array.prototype.map
- Array.prototype.pop
- Array.prototype.push
- Array.prototype.shift
- Array.prototype.slice
- Array.prototype.some
- Array.prototype.toString
- Boolean
- for loop
- for..in loop
- for..of loop
- String.prototype.split
- String.prototype.toLowerCase
- String.prototype.toUpperCase
- undefined
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