yves

A customizable value inspector for Node.js, inspired by eyes.

Handles circular objects, pretty-prints object literals, and supports ANSI color output, HTML output, and debug integration.

Install

npm install yves

Requires Node.js >= 18.

Usage

import yves from 'yves'

yves.inspect(something)

With a label:

yves.inspect(something, 'my value')

With a custom inspector:

const inspect = yves.inspector({ styles: { all: 'magenta' } })

inspect(something)

To return the string instead of printing to stdout:

const inspect = yves.inspector({ stream: null })

console.log(inspect({ something: 42 }))

Options

Pass options to inspector() or as the third argument to inspect().

Styles

styles: {
    all:     'cyan',      // Overall style applied to everything
    label:   'underline', // Inspection labels, like 'array' in `array: [1, 2, 3]`
    other:   'inverted',  // Objects without a literal representation (functions)
    key:     'bold',      // Object keys, like 'a' in `{a: 1}`
    special: 'grey',      // null, undefined
    string:  'green',
    number:  'magenta',
    bool:    'blue',
    regexp:  'green',
}

Available styles: bold, underline, inverse, cyan, magenta, blue, yellow, green, red, grey.

Set styles: false to disable all styling. Set colors: false to disable ANSI codes.

Formatting

Option	Default	Description
pretty	true	Indent object literals and arrays
indent	4	Spaces per indentation level
singleLineMax	2	Max keys before an object is printed multiline
trailingComma	true	Add trailing commas in multiline output
templateStrings	true	Use backtick syntax for strings containing newlines/tabs
escape	true	Escape invisible characters in strings
json	false	Use JSON-style output (double-quoted keys and strings)
sortKeys	false	Sort object keys alphabetically
sorted	false	Deep-sort the input object before inspecting

Truncation

Option	Default	Description
maxLength	-1	Max output length in characters (-1 for unlimited)
maxStringLength	-	Truncate strings beyond this length
maxArrayLength	-	Show at most N array elements
maxObjectKeys	-	Show at most N object keys

Filtering

Option	Default	Description
includes	null	Only show keys matching these strings/regexps
excludes	null	Hide keys matching these strings/regexps
obfuscates	null	Replace values of matching keys with <<obfuscated>>
hideFunctions	false	Omit function-valued properties

yves.inspect(obj, 'filtered', {
    includes: ['name', /^user/],
    obfuscates: ['password', /secret/],
})

Output

Option	Default	Description
stream	process.stdout	Writable stream, or null to return the string
colors	auto-detected	Enable ANSI color codes
html	false	Output HTML <span> tags instead of ANSI codes
decycle	true	Safely handle circular references

HTML output

const inspect = yves.inspector({ stream: null, html: true, colors: true })

const html = inspect({ hello: 'world' })
// Returns a <pre> block with <span> color styling

Debug integration

yves integrates with the debug module. Use the %y formatter for compact output or %Y for sorted, function-free output:

import debug from 'debug'
const log = debug('app')

log('user data: %y', userData)

Console hijacking

Replace console.log / console.dir etc. with yves-powered output routed through debug:

yves.console('myapp')

console.log('hello')   // now outputs via debug('myapp:console:log')
console.dir({ a: 1 })  // pretty-printed via yves

yves.console_unset()   // restore original console

API

• yves.inspect(obj, label?, options?) -- inspect and print to stream
• yves.inspector(options?) -- returns a reusable inspect function
• yves.options(opts) -- update global defaults
• yves.stylize(str, style, options) -- apply a single ANSI/HTML style
• yves.typeOf(value) -- enhanced typeof (distinguishes array, regexp, date, buffer, null, bigint)
• yves.debugger(namespace) -- create a debug logger
• yves.console(namespace?) -- hijack console with debug-powered output
• yves.console_unset() -- restore original console methods

License

MIT