analyze-css：CSS 选择器的复杂度和性能分析器_html/css_WEB-ITnose

CSS selectors complexity and performance analyzer. analyze-css is built as a set of rules bound to events fired by CSS parser. Each rule can generate metrics and add "offenders" with more detailed information (see Usage section for an example).

• Analyze CSS Demo

Install

analyze-css comes as a "binary" for command-line and as CommonJS module. Run the following to install them globally:

npm install --global analyze-css

Usage

Command line tool

You can use analyze-css "binary" to analyze local CSS files or remote CSS assets:

analyze-css --file examples/elecena.cssanalyze-css --url http://jigsaw.w3.org/css-validator/style/base.css

You can provide CSS via stdin as well (notice the dash: -):

echo ".foo {margin: 0 \!important}" | analyze-css -

This will emit JSON formatted results on stdout. Use --pretty (or -p shortcut) option to make the output readable for human beings.

Basic HTTP authentication can be provided through the options --auth-user and --auth-pass.

CommonJS module

var analyzer = require('analyze-css');new analyzer('.foo {margin: 0 !important}', function(err, results) {  console.error(err);  console.log(results); // example? see below});

// options can be providedvar opts = {  'noOffenders': true};new analyzer('.foo {margin: 0 !important}', opts, function(err, results) {  console.error(err);  console.log(results); // example? see below});```

grunt task

Created by @DeuxHuitHuit

npm i grunt-contrib-analyze-css

It uses configurable threshold and compares the analyze-css result with it.

Results

{  "generator": "analyze-css v0.8.0",  "metrics": {    "base64Length": 11332,    "redundantBodySelectors": 0,    "redundantChildNodesSelectors": 1,    "colors": 106,    "comments": 1,    "commentsLength": 68,    "complexSelectors": 37,    "complexSelectorsByAttribute": 3,    "duplicatedSelectors": 7,    "duplicatedProperties": 24,    "emptyRules": 0,    "expressions": 0,    "oldIEFixes": 51,    "imports": 0,    "importants": 3,    "mediaQueries": 0,    "multiClassesSelectors": 74,    "parsingErrors": 0,    "oldPropertyPrefixes": 79,    "propertyResets": 0,    "qualifiedSelectors": 28,    "specificityIdAvg": 0.04,    "specificityIdTotal": 25,    "specificityClassAvg": 1.27,    "specificityClassTotal": 904,    "specificityTagAvg": 0.79,    "specificityTagTotal": 562,    "selectors": 712,    "selectorLengthAvg": 1.5722460658082975,    "selectorsByAttribute": 92,    "selectorsByClass": 600,    "selectorsById": 25,    "selectorsByPseudo": 167,    "selectorsByTag": 533,    "universalSelectors": 5,    "length": 55173,    "rules": 433,    "declarations": 1288  },  "offenders": {    "importants": [      ".foo {margin: 0 !important}"    ]  }}

Metrics

• base64Length: total length of base64-encoded data in CSS source (will warn about base64-encoded data bigger than 4 kB)
• redundantBodySelectors: number of redundant body selectors (e.g. body .foo, section body h2, but not body > h1)
• redundantChildNodesSelectors: number of redundant child nodes selectors (e.g. ul li, table tr)
• colors: number of unique colors used in CSS
• comments: number of comments in CSS source
• commentsLength: length of comments content in CSS source
• complexSelectors: number of complex selectors (consisting of more than three expressions, e.g. header ul li .foo)
• complexSelectorsByAttribute: number of selectors with complex matching by attribute (e.g. [class$="foo"])
• duplicatedSelectors: number of CSS selectors defined more than once in CSS source
• duplicatedProperties: number of CSS property definitions duplicated within a selector
• emptyRules: number of rules with no properties (e.g. .foo { })
• expressions: number of rules with CSS expressions (e.g. expression( document.body.clientWidth > 600 ? "600px" : "auto" ))
• oldIEFixes: number of fixes for old versions of Internet Explorer (e.g. * html .foo {} and .foo { *zoom: 1 }, read more)
• imports number of @import rules
• importants: number of properties with value forced by !important
• mediaQueries: number of media queries (e.g. @media screen and (min-width: 1370px))
• multiClassesSelectors: reports selectors with multiple classes (e.g. span.foo.bar)
• parsingErrors: number of CSS parsing errors
• oldPropertyPrefixes: number of properties with no longer needed vendor prefix, powered by data provided by autoprefixer (e.g. --moz-border-radius)
• propertyResets: number of accidental property resets
• qualifiedSelectors: number of qualified selectors (e.g. header#nav, .foo#bar, h1.title)
• specificityIdAvg: average specificity for ID
• specificityIdTotal: total specificity for ID
• specificityClassAvg: average specificity for class, pseudo-class or attribute
• specificityClassTotal: total specificity for class, pseudo-class or attribute
• specificityTagAvg: average specificity for element
• specificityTagTotal: total specificity for element
• selectors: number of selectors (e.g. .foo, .bar { color: red } is counted as two selectors - .foo and .bar)
• selectorLengthAvg: average length of selector (e.g. for .foo .bar, #test div > span { color: red } will be set as 2.5)
• selectorsByAttribute: number of selectors by attribute (e.g. .foo[value=bar])
• selectorsByClass: number of selectors by class
• selectorsById: number of selectors by ID
• selectorsByPseudo: number of pseudo-selectors (e,g. :hover)
• selectorsByTag: number of selectors by tag name
• universalSelectors: number of selectors trying to match every element (e.g. .foo > *)
• length: length of CSS source (in bytes)
• rules: number of rules (e.g. .foo, .bar { color: red } is counted as one rule)
• declarations: number of declarations (e.g. .foo, .bar { color: red } is counted as one declaration - color: red)

Read more

• Writing Efficient CSS (by Mozilla)
• Optimize browser rendering (by Google)
• Profiling CSS for fun and profit. Optimization notes.
• CSS specificity
• CSS Selector Performance has changed! (For the better) (by Nicole Sullivan)
• CSS Performance (by Paul Irish)
• GitHub's CSS Performance (by Joh Rohan)

Dev hints

Running tests and linting the code:

npm test && npm run-script lint

Turning on debug mode (i.e. verbose logging to stderr via debug module):

DEBUG=analyze-css* analyze-css ...

项目地址： https://github.com/macbre/analyze-css