Package Exports

doiuse

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Readme

doiuse

Lint CSS for browser support against caniuse database.

NOTE: This is a very, very initial release. Feedback or contributions are quite welcome!

TL;DR

var postcss = require('postcss');
var doiuse = require('doiuse');

postcss(doiuse({
  browsers:['ie >= 6', '> 1%'],
  onUnsupportedFeatureUse: function(usageInfo) {
    
    // get human-readable list of browsers (from among those WE selected) that
    // don't support the given feature.
    var versions = usageInfo.featureData.missing;
    var browsers = [];
    for(browser in versions) {
      browsers.push(
        browser + ' (' + Object.keys(versions[browser]).join(',') + ')'
      );
    }
    
    // the location in the CSS file that triggered this callback
    var loc = usageInfo.usage.source;
    
    console.log(
      loc.id + ' line ' + loc.start.line + " : " + 
      usageInfo.feature + ' not supported by ' + browsers.join(',')
    );
  }
})).process("a { background-size: cover; }")

How it works

In particular, the approach to detecting features usage is currently quite naive.

Refer to the data in /src/data/features.coffee.

If a feature in that dataset only specifies properties, we just use those properties for substring matches against the properties used in the input CSS.
If a feature also specifies values, then we also require that the associated value matches one of those values (again, with a substring match).

TODO:

Selectors and @-rules
Allow each feature to have multiple instances of the match criteria laid out above, so that different, disjoint (property, value) combinations can be used to detect a feature.
Subfeatures, in to allow a slightly looser coupling with caniuse-db's structure (I'm thinking about the different versions of flexbox.)
Prefix-aware testing: i.e., pass along a list of prefixes used with a given feature. (This is low priority: just use autoprefixer.)

API Details:

postcss(doiuse(opts)).process(css), where opts is:

{
  browsers: ['ie >= 8', '> 1%'] // an autoprefixer-like array of browsers.
  onUnsupportedFeatureUse: function(usageInfo) { } // a callback for usages of features not supported by the selected browsers
}

And usageInfo looks like this:

{
  feature: 'css-gradients', //slug identifying a caniuse-db feature
  featureData:{
    missing: {
      // subset of selected browsers that are missing support for this
      // particular feature, mapped to the version and (lack of)support code
      ie: { '8': 'n' }
    },
    caniuseData: { // data from caniuse-db/features-json/[feature].json }
  },
  usage: //the postcss node where that feature is being used.
}

Called once for each usage of each css feature not supported by the selected
browsers.

License

MIT