Number vs. String

JavaScript FAQ | Numbers FAQ | Strings and RegExp FAQ  

Question: Is there a way to test whether a particular variable holds a number or a string?

Answer: Yes. To test whether the variable holds a number or a string, use the typeof operator. If your variable holds a number, typeof(variable) will return "number". If it holds a string, typeof(variable) will return "string". The following are examples of typeof usage:

typeof(123)    // result: "number"
typeof("123")  // result: "string"

if (typeof k == "string") { alert('k is a string.') }
if (typeof k == "number") { alert('k is a number.') }
The typeof operator can also help you distinguish between other data types. Depending on the particular variable's value, the result of typeof can be one of the following:

See also:

  • Converting numbers to strings
  • Converting strings to numbers
  • Converting a number to another base
  • Converting a string to URL-encoding
  • JavaScript number literals aka constants
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