The typeof operator, which also may be used as typeof(), provides a way to determine and to test the data type of a variable and may use either of the following notations, with or without parentheses.
var result = typeof variable
var result = typeof(variable)
After either line, the variable result is set to a string that is represents the variable's type: "undefined", "boolean", "string", "object", "number", or "function".
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