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+# postcss-values-parser  [![Build Status](https://travis-ci.org/shellscape/postcss-values-parser.svg?branch=master)](https://travis-ci.org/shellscape/postcss-values-parser)
+
+<img align="right" width="95" height="95"
+     title="Philosopher’s stone, logo of PostCSS"
+     src="http://postcss.github.io/postcss/logo.svg">
+
+A CSS property value parser for use with [PostCSS](https://github.com/postcss/postcss),
+following the same node, container, and traversal patterns as PostCSS.
+
+## &nbsp;
+<p align="center">
+  <b>:rocket: &nbsp; Are you ready to tackle ES6 and hone your JavaScript Skills?</b> &nbsp; :rocket:<br/>
+  Check out these outstanding <a href="https://es6.io/">ES6 courses</a> by <a href="https://github.com/wesbos">@wesbos</a>
+</p>
+
+---
+
+As with PostCSS and postcss-selector-parser, this parser generates an
+[Abstract Syntax Tree](https://en.wikipedia.org/wiki/Abstract_syntax_tree),
+(aka "AST") which allows for ease of traversal and granular inspection of each
+part of a property's value.
+
+## postcss-values-parser vs. postcss-value-parser
+
+Yeah, it's a tad confusing. The [Lesshint](https://github.com/lesshint/lesshint)
+project needed a parser that would allow detailed inspection of property values
+to the same degree that PostCSS and [postcss-selector-parser](https://github.com/postcss/postcss-selector-parser)
+provided. This was especailly important for the Lesshint project, as it provides
+for very granular rules for linting LESS.
+
+[postcss-value-parser](https://github.com/TrySound/postcss-value-parser)
+makes a lot of assumption about how values should be parsed and how the resulting
+AST should be organized. It was also fairly out of sync with the tokenzing and
+traversal patterns and convenience methods found in PostCSS and
+postcss-selector-parser.
+
+So we needed an alternative, and drew upon all three projects to put together a
+value parser that met and exceeded our needs. The improvements include:
+
+- Written using ES6
+- Uses the same Gulp toolchain as PostCSS
+- Doesn't strip characters; eg. parenthesis
+- Full AST traversal
+- AST traversal based on node type
+- Simple methods to derive strings from the parsed result
+- Follows PostCSS patterns for whitespace between Nodes
+- Provides convenience properties for number units, colors, etc.
+
+## Usage
+
+Please see the [API Documentation](API.md) for full usage information.
+
+As with any NPM module, start with the install:
+
+```
+npm install postcss-values-parser
+```
+
+Using this parser is straightforward and doesn't require callbacks:
+
+```js
+const parser = require('postcss-values-parser');
+const ast = parser('#fff').parse();
+
+let color = ast       // the Root node
+              .first  // the Value node
+              .first; // a Word node, containing the color value.
+```
+
+## Loose Mode
+
+Loose mode was introduced to support adherence to the W3C CSS Specification as
+well as the ability to parse noncompliant CSS for variants like LESS, SCSS, and
+CSSNext. If you're working with a noncompliant or CSS-like variant, then loose
+mode is for you.
+
+For example, the parser
+will throw an error by default if `calc` parameters [don't adhere to the spec](https://www.w3.org/TR/css-values/#calc-syntax).
+However, with loose mode enabled, the parse will ignore spec rules and succeed.
+
+In-draft features, or CSS features in modules not yet finalized, often cause parser
+errors. eg. `url(var(--somevar))`. Loose mode supports parsing of these features.
+
+Loose Mode is enabled by passing an option of `loose: true` to the `parser` method.
+
+```js
+const less = 'calc(2+2)'; // not valid per spec, but valid in LESS
+const cssnext = 'url(var(--somevar))'; // not valid per spec, but in spec draft
+
+const parser = require('postcss-values-parser');
+const ast = parser(less, { loose: true }).parse();
+
+// parse will succeed
+```
+
+## Acknowledgements
+
+This project was heavily influenced by [postcss-selector-parser](https://github.com/postcss/postcss-selector-parser)
+and utilized many patterns and logical constructs from the project.
+
+Tests and some tokenizing techniques found in [postcss-value-parser](https://github.com/TrySound/postcss-value-parser)
+were used.
+
+## Contributing
+
+- `git fork/clone`
+- `npm i`
+- Before PR'ing, make sure `npm test` still pass. Add test if you're adding features.
+
+When you tweak [API.md](API.md), please run `npm run toc` before PR'ing.