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178 lines
6.3 KiB
Markdown
178 lines
6.3 KiB
Markdown
# character-parser
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Parse JavaScript one character at a time to look for snippets in Templates. This is not a validator, it's just designed to allow you to have sections of JavaScript delimited by brackets robustly.
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[](https://travis-ci.org/ForbesLindesay/character-parser)
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## Installation
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npm install character-parser
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## Usage
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### Parsing
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Work out how much depth changes:
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```js
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var state = parse('foo(arg1, arg2, {\n foo: [a, b\n');
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assert.deepEqual(state.stack, [')', '}', ']']);
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parse(' c, d]\n })', state);
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assert.deepEqual(state.stack, []);
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```
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### Custom Delimited Expressions
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Find code up to a custom delimiter:
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```js
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// EJS-style
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var section = parser.parseUntil('foo.bar("%>").baz%> bing bong', '%>');
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assert(section.start === 0);
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assert(section.end === 17); // exclusive end of string
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assert(section.src = 'foo.bar("%>").baz');
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var section = parser.parseUntil('<%foo.bar("%>").baz%> bing bong', '%>', {start: 2});
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assert(section.start === 2);
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assert(section.end === 19); // exclusive end of string
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assert(section.src = 'foo.bar("%>").baz');
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// Jade-style
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var section = parser.parseUntil('#[p= [1, 2][i]]', ']', {start: 2})
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assert(section.start === 2);
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assert(section.end === 14); // exclusive end of string
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assert(section.src === 'p= [1, 2][i]')
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// Dumb parsing
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// Stop at first delimiter encountered, doesn't matter if it's nested or not
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// This is the character-parser@1 default behavior.
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var section = parser.parseUntil('#[p= [1, 2][i]]', '}', {start: 2, ignoreNesting: true})
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assert(section.start === 2);
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assert(section.end === 10); // exclusive end of string
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assert(section.src === 'p= [1, 2')
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''
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```
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Delimiters are ignored if they are inside strings or comments.
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## API
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All methods may throw an exception in the case of syntax errors. The exception contains an additional `code` property that always starts with `CHARACTER_PARSER:` that is unique for the error.
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### parse(str, state = defaultState(), options = {start: 0, end: src.length})
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Parse a string starting at the index start, and return the state after parsing that string.
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If you want to parse one string in multiple sections you should keep passing the resulting state to the next parse operation.
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Returns a `State` object.
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### parseUntil(src, delimiter, options = {start: 0, ignoreLineComment: false, ignoreNesting: false})
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Parses the source until the first occurence of `delimiter` which is not in a string or a comment.
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If `ignoreLineComment` is `true`, it will still count if the delimiter occurs in a line comment.
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If `ignoreNesting` is `true`, it will stop at the first bracket, not taking into account if the bracket part of nesting or not. See example above.
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It returns an object with the structure:
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```js
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{
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start: 0,//index of first character of string
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end: 13,//index of first character after the end of string
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src: 'source string'
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}
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```
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### parseChar(character, state = defaultState())
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Parses the single character and returns the state. See `parse` for the structure of the returned state object. N.B. character must be a single character not a multi character string.
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### defaultState()
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Get a default starting state.
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### isPunctuator(character)
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Returns `true` if `character` represents punctuation in JavaScript.
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### isKeyword(name)
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Returns `true` if `name` is a keyword in JavaScript.
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### TOKEN_TYPES & BRACKETS
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Objects whose values can be a frame in the `stack` property of a State (documented below).
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## State
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A state is an object with the following structure
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```js
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{
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stack: [], // stack of detected brackets; the outermost is [0]
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regexpStart: false, // true if a slash is just encountered and a REGEXP state has just been added to the stack
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escaped: false, // true if in a string and the last character was an escape character
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hasDollar: false, // true if in a template string and the last character was a dollar sign
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src: '', // the concatenated source string
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history: '', // reversed `src`
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lastChar: '' // last parsed character
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}
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```
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`stack` property can contain any of the following:
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- Any of the property values of `characterParser.TOKEN_TYPES`
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- Any of the property values of `characterParser.BRACKETS` (the end bracket, not the starting bracket)
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It also has the following useful methods:
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- `.current()` returns the innermost bracket (i.e. the last stack frame).
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- `.isString()` returns `true` if the current location is inside a string.
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- `.isComment()` returns `true` if the current location is inside a comment.
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- `.isNesting([opts])` returns `true` if the current location is not at the top level, i.e. if the stack is not empty. If `opts.ignoreLineComment` is `true`, line comments are not counted as a level, so for `// a` it will still return false.
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### Errors
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All errors thrown by character-parser has a `code` property attached to it that allows one to identify what sort of error is thrown. For errors thrown from `parse` and `parseUntil`, an additional `index` property is available.
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## Transition from v1
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In character-parser@2, we have changed the APIs quite a bit. These are some notes that will help you transition to the new version.
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### State Object Changes
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Instead of keeping depths of different brackets, we are now keeping a stack. We also removed some properties:
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```js
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state.lineComment → state.current() === parser.TOKEN_TYPES.LINE_COMMENT
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state.blockComment → state.current() === parser.TOKEN_TYPES.BLOCK_COMMENT
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state.singleQuote → state.current() === parser.TOKEN_TYPES.SINGLE_QUOTE
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state.doubleQuote → state.current() === parser.TOKEN_TYPES.DOUBLE_QUOTE
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state.regexp → state.current() === parser.TOKEN_TYPES.REGEXP
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```
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### `parseMax`
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This function has been removed since the usefulness of this function has been questioned. You should find that `parseUntil` is a better choice for your task.
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### `parseUntil`
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The default behavior when the delimiter is a bracket has been changed so that nesting is taken into account to determine if the end is reached.
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To preserve the original behavior, pass `ignoreNesting: true` as an option.
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To see the difference between the new and old behaviors, see the "Usage" section earlier.
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### `parseMaxBracket`
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This function has been merged into `parseUntil`. You can directly rename the function call without any repercussions.
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## License
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MIT
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