Today I Learned - Rocky Kev

TIL Double Exclamation shorthand for booleans

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TAGS: javascript booleans

Javascript follows Truthy/Falsy values.

If you're not familiar with it:

(Via Wes Bos)

But if you want to make it explicit:

JavaScript (and TypeScript) lets you convert a non-Boolean value to Boolean using the double exclamation shorthand.

const emptyStr = ''
const nonEmptyStr = 'test'

const emptyStrBool = !!emptyStr //false
const nonEmptyStrBool = !!nonEmptyStr //true

via Understanding the exclamation mark in TypeScript

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