JavaScript instance tutorial: typeof operator

Source: Internet
Author: User
Tags numeric numeric value

Since ECMAScript is loosely typed, there is a need to have a means to detect the data type of a given variable--typeof is the operator responsible for providing this convenient information. Using the typeof operator on a value may return one of the following strings:

"Undefined"--if this value is not defined

"Boolean"--if this value is a Boolean value

"String"--if this value is a string

"Number"--if this is a numeric value

"Object"--if this is an object or null

"Function"--if this value is a function

Here are a few examples of using the TypeOf operator:

var message = "some string";

Alert (typeof message); "String"

Alert (typeof (Message)); "String"

Alert (typeof 95); "Number"

These examples show that the operands of the typeof operator can be either a variable (message) or a numeric literal. Note that TypeOf is an operator rather than a function, so the parentheses in the example are not required (although they can be used).

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