'tis

Type safe variable checks

Install

npm i @jakesidsmith/tis -P

-P is shorthand for --save-production and will add this to your package dependencies.

Use -D (shorthand for --save-dev) if you are only using this for testing.

Available utilities

• isNumber: Returns true when the input is a number
• isString: Returns true when the input is a string
• isBoolean: Returns true when the input is a boolean
• isUndefined: Returns true when the input is undefined
• isDefined: Returns true when the input is not undefined
• isNull: Returns true when the input is null
• isNullish: Returns true when the input is null or undefined
• isArray: Returns true when the input is an array
• isObject: Returns true when the input is an object (includes arrays, excludes null)
• isFunction: Returns true when the input is a function or class constructor

Example usage

import { isObject, isArray, isString } from '@jakesidsmith/tis';

const example = (
  input: string | number | readonly string[] | Record<string, string>
) => {
  if (isObject(input)) {
    if (isArray(input)) {
      // Guaranteed to be a readonly string[]
    } else {
      // Guaranteed to be a Record<string, string>
    }
  } else if (isString(input)) {
    // Guaranteed to be a string
  } else {
    // Guaranteed to be a number
  }
};