How to check if type is Boolean

Question

How can I check if a variable\'s type is of type Boolean?

I mean, there are some alternatives such as:

if(jQuery.type(new Boolean()) === jQuery.type(         


        

Answer 1

• The most readable: val === false || val === true.
• Also readable: typeof variable == typeof true.

• The shortest, but not readable at all: !!val === val.

  Explanation:

  • [!!] The double exclamation mark converts the value into a Boolean.
  • [===] The triple equals test for strict equality: both the type (Boolean) and the value have to be the same.
  • If the original value is not a Boolean one, it won't pass the triple equals test. If it is a Boolean variable, it will pass the triple equals test (with both type & value).

  Tests:

  • !!5 === 5 // false
  • !!'test' === 'test' // false
  • let val = new Date(); !!val === val // false
  • !!true === true // true
  • !!false === false // true