Skip to main content
This codemod replaces the following deprecated util.is*() methods with their modern equivalents.

​
What It Does

This codemod handles 15 deprecated type-checking methods:
  • util.isArray() → Array.isArray()
  • util.isBoolean() → typeof value === 'boolean'
  • util.isBuffer() → Buffer.isBuffer()
  • util.isDate() → value instanceof Date
  • util.isError() → Error.isError()
  • util.isFunction() → typeof value === 'function'
  • util.isNull() → value === null
  • util.isNullOrUndefined() → value === null || value === undefined
  • util.isNumber() → typeof value === 'number'
  • util.isObject() → value && typeof value === 'object'
  • util.isPrimitive() → Object(value) !== value
  • util.isRegExp() → value instanceof RegExp
  • util.isString() → typeof value === 'string'
  • util.isSymbol() → typeof value === 'symbol'
  • util.isUndefined() → typeof value === 'undefined'

​
Before/After Examples

​
Type Checks

Before: 
const util = require('node:util');

if (util.isArray(value)) { }
if (util.isString(value)) { }
if (util.isNumber(value)) { }
After: 
if (Array.isArray(value)) { }
if (typeof value === 'string') { }
if (typeof value === 'number') { }

​
Object Type Checks

Before: 
const util = require('node:util');

if (util.isDate(value)) { }
if (util.isRegExp(value)) { }
if (util.isBuffer(value)) { }
After: 
if (value instanceof Date) { }
if (value instanceof RegExp) { }
if (Buffer.isBuffer(value)) { }

​
Null/Undefined Checks

Before: 
const util = require('node:util');

if (util.isNull(value)) { }
if (util.isUndefined(value)) { }
if (util.isNullOrUndefined(value)) { }
After: 
if (value === null) { }
if (typeof value === 'undefined') { }
if (value === null || value === undefined) { }

​
Usage

Run this codemod on your project: 
npx codemod node/userland/util-is
Modern JavaScript provides native type-checking mechanisms that are more performant and widely understood. These standard approaches are preferred over Node.js-specific utilities.

Build docs developers (and LLMs) love

Get started for freeTalk to us