util.isDate(object) Stability: 0 - Deprecated Returns true if the given "object" is a Date. Otherwise, returns false. const util = require('util'); util.isDate(new Date()) // true util.isDate(Date()) // false (without 'new' returns a String) util.isDate({}) // false

util.isBuffer(object) Stability: 0 - Deprecated: Use Buffer.isBuffer() instead. Returns true if the given "object" is a Buffer. Otherwise, returns false. const util = require('util'); util.isBuffer({ length: 0 }) // false util.isBuffer([]) // false util.isBuffer(new Buffer('hello world')) // true

util.isBoolean(object) Stability: 0 - Deprecated Returns true if the given "object" is a Boolean. Otherwise, returns false. const util = require('util'); util.isBoolean(1) // false util.isBoolean(0) // false util.isBoolean(false) // true

util.isArray(object) Stability: 0 - Deprecated Internal alias for Array.isArray. Returns true if the given "object" is an Array. Otherwise, returns false. const util = require('util'); util.isArray([]) // true util.isArray(new Array) // true util.isArray({}) // false

util.inspect(object[, options]) Return a string representation of object, which is useful for debugging. An optional options object may be passed that alters certain aspects of the formatted string: showHidden - if true then the object's non-enumerable and symbol properties will be shown too. Defaults to false. depth - tells inspect how many times to recurse while formatting the object. This is useful for inspecting large complicated objects. Defaults to 2. To make it recurse indefinitely

util.inherits(constructor, superConstructor) Inherit the prototype methods from one constructor into another. The prototype of constructor will be set to a new object created from superConstructor. As an additional convenience, superConstructor will be accessible through the constructor.super_ property. const util = require('util'); const EventEmitter = require('events'); function MyStream() { EventEmitter.call(this); } util.inherits(MyStream, EventEmitter); MyStream.prototype.write =

util.format(format[, ...]) Returns a formatted string using the first argument as a printf-like format. The first argument is a string that contains zero or more placeholders. Each placeholder is replaced with the converted value from its corresponding argument. Supported placeholders are: %s - String. %d - Number (both integer and float). %j - JSON. Replaced with the string '[Circular]' if the argument contains circular references. %% - single percent sign ('%'). This does not consume an

util.error([...]) Stability: 0 - Deprecated: Use console.error() instead. Deprecated predecessor of console.error.

util.deprecate(function, string) Marks that a method should not be used any more. const util = require('util'); exports.puts = util.deprecate(() => { for (var i = 0, len = arguments.length; i < len; ++i) { process.stdout.write(arguments[i] + '\n'); } }, 'util.puts: Use console.log instead'); It returns a modified function which warns once by default. If --no-deprecation is set then this function is a NO-OP. Configurable at run-time through the process.noDeprecation boolean (onl

util.debuglog(section) section <String> The section of the program to be debugged Returns: <Function> The logging function This is used to create a function which conditionally writes to stderr based on the existence of a NODE_DEBUG environment variable. If the section name appears in that environment variable, then the returned function will be similar to console.error(). If not, then the returned function is a no-op. For example: var debuglog = util.debuglog('foo'); var bar