flow-typer-js/dist/is.js.flow

Declarative static and runtime type checking with Flow

// @flow

export const isNil =
  (v: mixed) /*: v is null */ =>
    v === null

export const isUndef =
  (v: mixed) /*: v is void */ =>
    typeof v === 'undefined'

export const isBoolean =
  (v: mixed) /*: v is boolean */ =>
    typeof v === 'boolean'

export const isNumber =
  (v: mixed) /*: v is number */ =>
    typeof v === 'number'

export const isString =
  (v: mixed) /*: v is string */ =>
    typeof v === 'string'

export const isObject =
  (v: mixed) /*: v is {...} */ =>
    v !== null && typeof v === 'object'