Print

Generates a diff-friendly, human-readable representation of a JavaScript object. Ideal for preparing AssertionError feedback, or for inspecting objects in environments where Node's util.inspect() is unavailable.

Usage

import print from "./print.mjs";

let result;
result = print(subject);
result = print(subject, options);
result = print(subject, "label");
result = print(subject, "label", options);

print() returns a string containing an unambiguous representation of an object or primitive, optionally prefixed with a label. The output format depends on the subject's type, the presence or absence of properties, and options set by the user.

subject

• Type: Any
• Default: undefined

The JavaScript value being printed.

label

• Type: String | Symbol
• Default: "{root}"

The name of a property (or variable) that subject is associated with. This can improve readability of object references (indicated by ->), or clarify context by prefixing output with a meaningful label.

const targetObject = {
	foo: {},
	bar: {},
};
targetObject.bar.referenceToFoo = targetObject.foo;
print(targetObject, "subject");

The example above returns:

subject: {
	foo: {}
	bar: {
		referenceToFoo: -> subject.foo
	}
}

options

• Type: Object
• Default: {}

Additional settings for refining output. Unless mentioned otherwise, all options default to null or false.

Name	Type	Description
all	Boolean	Display non-enumerable properties
attr	Boolean	Display property attributes as <W,E,C>
followGetters	Boolean	Invoke getter functions
indent	String	String (or num. of spaces) used to indent
indexes	Boolean	Display the indexes of iterable entries
maxDepth	Number	Hide object details after N recursions
noAmp	Boolean	Don't format well-known symbols as @@…
noHex	Boolean	Don't format byte-arrays as hexadecimal
noSource	Boolean	Don't display function source code
proto	Boolean	Show __proto__ properties if possible
sort	Boolean	Sort properties alphabetically

To-do list

• Add options for…
  • Annotating property attributes (writable, enumerable, configurable)
  • maxLines/maxSize for truncating length arrays or strings
• Document remaining options
• Migrate to GitHub Actions
• Shorten sortProps to just sort