# jsonc-parser
Scanner and parser for JSON with comments.
[](https://www.npmjs.org/package/jsonc-parser)
[](https://npmjs.org/package/jsonc-parser)
[](https://travis-ci.org/Microsoft/node-jsonc-parser)
Why?
----
JSONC is JSON with JavaScript style comments. This node module provides a scanner and fault tolerant parser that can process JSONC but is also useful for standard JSON.
- the *scanner* tokenizes the input string into tokens and token offsets
- the *visit* function implements a 'SAX' style parser with callbacks for the encountered properties and values.
- the *parseTree* function computes a hierarchical DOM with offsets representing the encountered properties and values.
- the *parse* function evaluates the JavaScript object represented by JSON string in a fault tolerant fashion.
- the *getLocation* API returns a location object that describes the property or value located at a given offset in a JSON document.
- the *findNodeAtLocation* API finds the node at a given location path in a JSON DOM.
- the *format* API computes edits to format a JSON document.
- the *modify* API computes edits to insert, remove or replace a property or value in a JSON document.
- the *applyEdits* API applies edits to a document.
Installation
------------
```
npm install --save jsonc-parser
```
API
---
### Scanner:
```typescript
/**
* Creates a JSON scanner on the given text.
* If ignoreTrivia is set, whitespaces or comments are ignored.
*/
export function createScanner(text: string, ignoreTrivia: boolean = false): JSONScanner;
/**
* The scanner object, representing a JSON scanner at a position in the input string.
*/
export interface JSONScanner {
/**
* Sets the scan position to a new offset. A call to 'scan' is needed to get the first token.
*/
setPosition(pos: number): any;
/**
* Read the next token. Returns the token code.
*/
scan(): SyntaxKind;
/**
* Returns the zero-based current scan position, which is after the last read token.
*/
getPosition(): number;
/**
* Returns the last read token.
*/
getToken(): SyntaxKind;
/**
* Returns the last read token value. The value for strings is the decoded string content. For numbers it's of type number, for boolean it's true or false.
*/
getTokenValue(): string;
/**
* The zero-based start offset of the last read token.
*/
getTokenOffset(): number;
/**
* The length of the last read token.
*/
getTokenLength(): number;
/**
* The zero-based start line number of the last read token.
*/
getTokenStartLine(): number;
/**
* The zero-based start character (column) of the last read token.
*/
getTokenStartCharacter(): number;
/**
* An error code of the last scan.
*/
getTokenError(): ScanError;
}
```
### Parser:
```typescript
export interface ParseOptions {
disallowComments?: boolean;
allowTrailingComma?: boolean;
allowEmptyContent?: boolean;
}
/**
* Parses the given text and returns the object the JSON content represents. On invalid input, the parser tries to be as fault tolerant as possible, but still return a result.
* Therefore always check the errors list to find out if the input was valid.
*/
export declare function parse(text: string, errors?: {error: ParseErrorCode;}[], options?: ParseOptions): any;
/**
* Parses the given text and invokes the visitor functions for each object, array and literal reached.
*/
export declare function visit(text: string, visitor: JSONVisitor, options?: ParseOptions): any;
/**
* Visitor called by {@linkcode visit} when parsing JSON.
*
* The visitor functions have the following common parameters:
* - `offset`: Global offset within the JSON document, starting at 0
* - `startLine`: Line number, starting at 0
* - `startCharacter`: Start character (column) within the current line, starting at 0
*
* Additionally some functions have a `pathSupplier` parameter which can be used to obtain the
* current `JSONPath` within the document.
*/
export interface JSONVisitor {
/**
* Invoked when an open brace is encountered and an object is started. The offset and length represent the location of the open brace.
*/
onObjectBegin?: (offset: number, length: number, startLine: number, startCharacter: number, pathSupplier: () => JSONPath) => void;
/**
* Invoked when a property is encountered. The offset and length represent the location of the property name.
* The `JSONPath` created by the `pathSupplier` refers to the enclosing JSON object, it does not include the
* property name yet.
*/
onObjectProperty?: (property: string, offset: number, length: number, startLine: number, startCharacter: number, pathSupplier: () => JSONPath) => void;
/**
* Invoked when a closing brace is encountered and an object is completed. The offset and length represent the location of the closing brace.
*/
onObjectEnd?: (offset: number, length: number, startLine: number, startCharacter: number) => void;
/**
* Invoked when an open bracket is encountered. The offset and length represent the location of the open bracket.
*/
onArrayBegin?: (offset: number, length: number, startLine: number, startCharacter: number, pathSupplier: () => JSONPath) => void;
/**
* Invoked when a closing bracket is encountered. The offset and length represent the location of the closing bracket.
*/
onArrayEnd?: (offset: number, length: number, startLine: number, startCharacter: number) => void;
/**
* Invoked when a literal value is encountered. The offset and length represent the location of the literal value.
*/
onLiteralValue?: (value: any, offset: number, length: number, startLine: number, startCharacter: number, pathSupplier: () => JSONPath) => void;
/**
* Invoked when a comma or colon separator is encountered. The offset and length represent the location of the separator.
*/
onSeparator?: (character: string, offset: number, length: number, startLine: number, startCharacter: number) => void;
/**
* When comments are allowed, invoked when a line or block comment is encountered. The offset and length represent the location of the comment.
*/
onComment?: (offset: number, length: number, startLine: number, startCharacter: number) => void;
/**
* Invoked on an error.
*/
onError?: (error: ParseErrorCode, offset: number, length: number, startLine: number, startCharacter: number) => void;
}
/**
* Parses the given text and returns a tree representation the JSON content. On invalid input, the parser tries to be as fault tolerant as possible, but still return a result.
*/
export declare function parseTree(text: string, errors?: ParseError[], options?: ParseOptions): Node | undefined;
export declare type NodeType = "object" | "array" | "property" | "string" | "number" | "boolean" | "null";
export interface Node {
type: NodeType;
value?: any;
offset: number;
length: number;
colonOffset?: number;
parent?: Node;
children?: Node[];
}
```
### Utilities:
```typescript
/**
* Takes JSON with JavaScript-style comments and remove
* them. Optionally replaces every none-newline character
* of comments with a replaceCharacter
*/
export declare function stripComments(text: string, replaceCh?: string): string;
/**
* For a given offset, evaluate the location in the JSON document. Each segment in the location path is either a property name or an array index.
*/
export declare function getLocation(text: string, position: number): Location;
/**
* A {@linkcode JSONPath} segment. Either a string representing an object property name
* or a number (starting at 0) for array indices.
*/
export declare type Segment = string | number;
export declare type JSONPath = Segment[];
export interface Location {
/**
* The previous property key or literal value (string, number, boolean or null) or undefined.
*/
previousNode?: Node;
/**
* The path describing the location in the JSON document. The path consists of a sequence strings
* representing an object property or numbers for array indices.
*/
path: JSONPath;
/**
* Matches the locations path against a pattern consisting of strings (for properties) and numbers (for array indices).
* '*' will match a single segment, of any property name or index.
* '**' will match a sequence of segments or no segment, of any property name or index.
*/
matches: (patterns: JSONPath) => boolean;
/**
* If set, the location's offset is at a property key.
*/
isAtPropertyKey: boolean;
}
/**
* Finds the node at the given path in a JSON DOM.
*/
export function findNodeAtLocation(root: Node, path: JSONPath): Node | undefined;
/**
* Finds the most inner node at the given offset. If includeRightBound is set, also finds nodes that end at the given offset.
*/
export function findNodeAtOffset(root: Node, offset: number, includeRightBound?: boolean) : Node | undefined;
/**
* Gets the JSON path of the given JSON DOM node
*/
export function getNodePath(node: Node): JSONPath;
/**
* Evaluates the JavaScript object of the given JSON DOM node
*/
export function getNodeValue(node: Node): any;
/**
* Computes the edit operations needed to format a JSON document.
*
* @param documentText The input text
* @param range The range to format or `undefined` to format the full content
* @param options The formatting options
* @returns The edit operations describing the formatting changes to the original document following the format described in {@linkcode EditResult}.
* To apply the edit operations to the input, use {@linkcode applyEdits}.
*/
export function format(documentText: string, range: Range, options: FormattingOptions): EditResult;
/**
* Computes the edit operations needed to modify a value in the JSON document.
*
* @param documentText The input text
* @param path The path of the value to change. The path represents either to the document root, a property or an array item.
* If the path points to an non-existing property or item, it will be created.
* @param value The new value for the specified property or item. If the value is undefined,
* the property or item will be removed.
* @param options Options
* @returns The edit operations describing the changes to the original document, following the format described in {@linkcode EditResult}.
* To apply the edit operations to the input, use {@linkcode applyEdits}.
*/
export function modify(text: string, path: JSONPath, value: any, options: ModificationOptions): EditResult;
/**
* Applies edits to an input string.
* @param text The input text
* @param edits Edit operations following the format described in {@linkcode EditResult}.
* @returns The text with the applied edits.
* @throws An error if the edit operations are not well-formed as described in {@linkcode EditResult}.
*/
export function applyEdits(text: string, edits: EditResult): string;
/**
* An edit result describes a textual edit operation. It is the result of a {@linkcode format} and {@linkcode modify} operation.
* It consist of one or more edits describing insertions, replacements or removals of text segments.
* * The offsets of the edits refer to the original state of the document.
* * No two edits change or remove the same range of text in the original document.
* * Multiple edits can have the same offset if they are multiple inserts, or an insert followed by a remove or replace.
* * The order in the array defines which edit is applied first.
* To apply an edit result use {@linkcode applyEdits}.
* In general multiple EditResults must not be concatenated because they might impact each other, producing incorrect or malformed JSON data.
*/
export type EditResult = Edit[];
/**
* Represents a text modification
*/
export interface Edit {
/**
* The start offset of the modification.
*/
offset: number;
/**
* The length of the modification. Must not be negative. Empty length represents an *insert*.
*/
length: number;
/**
* The new content. Empty content represents a *remove*.
*/
content: string;
}
/**
* A text range in the document
*/
export interface Range {
/**
* The start offset of the range.
*/
offset: number;
/**
* The length of the range. Must not be negative.
*/
length: number;
}
/**
* Options used by {@linkcode format} when computing the formatting edit operations
*/
export interface FormattingOptions {
/**
* If indentation is based on spaces (`insertSpaces` = true), then what is the number of spaces that make an indent?
*/
tabSize: number;
/**
* Is indentation based on spaces?
*/
insertSpaces: boolean;
/**
* The default 'end of line' character
*/
eol: string;
}
/**
* Options used by {@linkcode modify} when computing the modification edit operations
*/
export interface ModificationOptions {
/**
* Formatting options. If undefined, the newly inserted code will be inserted unformatted.
*/
formattingOptions?: FormattingOptions;
/**
* Default false. If `JSONPath` refers to an index of an array and `isArrayInsertion` is `true`, then
* {@linkcode modify} will insert a new item at that location instead of overwriting its contents.
*/
isArrayInsertion?: boolean;
/**
* Optional function to define the insertion index given an existing list of properties.
*/
getInsertionIndex?: (properties: string[]) => number;
}
```
License
-------
(MIT License)
Copyright 2018, Microsoft