Knowledge Base: JavaScript Engine

As mentioned before, RavenDB uses Jint to execute JavaScript code in a variety of operations.
In order to perform an operation, Jint receives a function to run and a single document to process, therefore, the processing context of Jint is a single document and there is no "long-term" execution context, even when it may look like it, in patch operations.
Jint engine initialization is an expansive operation, therefore, RavenDB caches Jint instances according to the user defined scripts and reuses them.

RavenDB introduced a set of predefined function, in addition to Jint's ECMAScript.1 implementation.

Method Signature	Return type	Description
id(document)	string	Returns document's ID.
load(documentId)	object	Returns the document with the given ID.
loadPath(document, pathString)	Task	Returns the document(s) according to the IDs that can be found in the given document, in the path pathString. The pathString can be of a simple Foo.Bar form, in that case, a single document will be returned. It also be of the form Foo.Bars[].Buzz, in that case it will return an array of documents, answering the path .
cmpxchg(compareExchangeKey)	object	Returns stored Compare Exchange value for the received key.
getMetadata(document)	object	Returns document's metadata, along with it's ChangeVector, ID and LastModified.
lastModified(document)	long	Returns document's last modified metadata value as total miliseconds of UTC .
include(documentId)	Task<string>	Used for RQL queries in order to include the document with the given ID with the results
del(documentId)	void	Used in patches, deletes the document with the given ID.
put(documentId, document, [optional]changeVectorString)	Task	Used in patches, creates or updates a document with the given ID. In order to generate a new document ID it's possible to use "[collectionPrefix]/" Server-Side ID notation[ex]. This function can also be used to clone an existing document (Note: Attachments will not be attached to the clone)[ex].
String.prototype.startsWith(searchString, position)	bool	Returns true if at position the string starts with searchString.
String.prototype.endsWith(searchString, position)	bool	Returns true if at position the string end with searchString .
String.prototype.padStart(targetLength, padString)	string	Returns a new string, that padded from it's start by the string padString(or white-space by default), until it reaches the length targetlength. The function will repeat padString if needed.
String.prototype.padEnd(targetLength, padString)	string	Returns a new string, that padded from it's end by the string padString(or white-space by default), until it reaches the length targetlength. The function will repeat padString if needed.
String.prototype.format(arg1, arg2, arg3 ...)	string	Returns "formatted" string, that replaces all occurrences of {[number]} with an argument in the numbers place (using a zero based index).
startsWith(inputString, prefix)	bool	Returns true if inputStringstarts with prefix.
endsWith(inputString, suffix)	bool	Returns true if inputString ends with suffix.
regex(inputString, regex)	bool	Returns true if inputString matches regex regular expression.
Array.prototype.find(function callback)	Array's element	Returns the first array element, for which the callback function returns true.
Object.map(input, function mapFunction, context)	Array	Returns an array containing result of mapFunction process result of all input's properties (items, if it's an array). The mapFunction's signature is function(itemValue, itemKey)
Raven_Min(num1, num2)	bool	Find minimum out of num1 and num2. Parameters can be numbers or strings, but there is no raw number support (see scalarToRawString below). Strings will be parsed to double upon processing
Raven_Max(num1, num2)	bool	Find maximum out of num1 and num2. Parameters can be numbers or strings, but there is no raw number support (see scalarToRawString below). Strings will be parsed to double upon processing
convertJsTimeToTimeSpanString(ticksNumber)	bool	Returns human readable TimeSpan of the received ticksNumber.
scalarToRawString(document, lambdaToField)	Raw field value (LazyStringValue for strings, LazyNumberValue for floating point numbers).	Returns raw representation of a field. Useful when working with numbers that exceeds double's numeric or accuracy range. See Numbers in Jint. Also usefull for better memory consumption when projecting big string values. Note: returned value is immutable
output(message)	void	Used for single document patches debug.