JavaScript Built In Operator -- (Decrement Prefix)

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This is an operator designated for decrementing a value in math within JavaScript. This method is called prefix (the -- before the variable), there is a more common postfix method also which is slightly different. In the prefix operator, the increment takes place before the number or variable is used. Within parenthesis, they are the same. In an equation without parenthesis surrounding it, prefix or postfix precedence takes place. Compare this to Increment postfix.