Get the type of a variable as a string

Read the internal [[Class]] tag via Object.prototype.toString.

JavaScript Version 1.0.0 · MIT · .md

function getTypeOf(value) { return Object.prototype.toString.call(value).match(/\[object (.*)\]/)[1]; }

Input & expected output

[
  1,
  2
]

"Array"

The edge case

null

"Null"

Know the limits

• Distinguishes Array, Null, Date and RegExp where typeof says "object". Objects can override the tag with Symbol.toStringTag.

The function above is the implementation used by the lab. The lab validates JSON types and caps size before execution; include equivalent validation when accepting untrusted input in your application.

Keep exploring

• Convert Celsius to Fahrenheit — Apply the temperature conversion without rounding the result.
• Convert hex to RGB — Expand #rgb if needed and read the red, green and blue channels.
• Convert URL parameters to object — Read a query string into an object; repeated keys become arrays.