68 lines
1.7 KiB
Markdown
68 lines
1.7 KiB
Markdown
# token-stream
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Take an array of token and produce a more useful API to give to a parser.
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[](https://travis-ci.org/pugjs/token-stream)
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[](https://david-dm.org/pugjs/token-stream)
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[](https://www.npmjs.org/package/token-stream)
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## Installation
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npm install token-stream
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## Usage
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```js
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var TokenStream = require('token-stream');
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var stream = new TokenStream([
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'a',
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'b',
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'c',
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'd'
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]);
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assert(stream.peek() === 'a');
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assert(stream.lookahead(0) == 'a');
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assert(stream.lookahead(1) == 'b');
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assert(stream.advance() === 'a');
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assert(stream.peek() === 'b');
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assert(stream.lookahead(0) == 'b');
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assert(stream.lookahead(1) == 'c');
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stream.defer('z');
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assert(stream.peek() === 'z');
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assert(stream.lookahead(0) == 'z');
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assert(stream.lookahead(1) == 'b');
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assert(stream.advance() === 'z');
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assert(stream.advance() === 'b');
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assert(stream.advance() === 'c');
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assert(stream.advance() === 'd');
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// an error is thrown if you try and advance beyond the end of the stream
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assert.throws(function () {
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stream.advance();
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});
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```
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## API
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### stream.peek()
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Gets and returns the next item in the stream without advancing the stream's position.
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### stream.advance()
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Returns the next item in the stream and advances the stream by one item.
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### stream.defer(token)
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Put a token on the start of the stream (useful if you need to back track after calling advance).
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### stream.lookahead(index)
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Return the item at `index` position from the start of the stream, but don't advance the stream. `stream.lookahead(0)` is equivalent to `stream.peek()`.
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## License
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MIT
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