compact array of props

lib/index.js

@@ -1,9 +1,23 @@
-var ASSERT = require('assert');
 var list = require('./list');
-var props = require('css-shorthand-properties').shorthandProperties;
+var shorthandProps = require('css-shorthand-properties').shorthandProperties;
 
 exports.isShorthand = isShorthand;
 exports.expand = expand;
+exports.isCompactable = isCompactable;
+exports.compact = compact;
+
+var invertedShorthandProps = Object.keys(shorthandProps)
+    .reduce(function(inverted, shorthand) {
+        expandAsArray(shorthand, false).forEach(function(key) {
+            inverted[key] = shorthand;
+        });
+        return inverted;
+    }, {})
+
+var errors = {
+    noPropertyArg: 'property argument is required',
+    propsArentCompactable: 'properties aren\'t compactable'
+}
 
 /**
  * Expand a property to an array of parts or property and value to object
@@ -14,7 +28,7 @@ exports.expand = expand;
  * @returns {Array|Object}
  */
 function expand(property, value, recurse) {
-    ASSERT(arguments.length, 'property argument is required');
+    if (!arguments.length) throw new Error(erros.noPropertyArg);
 
     if (arguments.length < 3) {
         if (typeof value === 'boolean') {
@@ -33,11 +47,11 @@ function expand(property, value, recurse) {
 }
 
 function expandAsArray(property, recurse) {
-    if (!props.hasOwnProperty(property)) {
+    if (!shorthandProps.hasOwnProperty(property)) {
         return [property];
     }
 
-    return props[property]
+    return shorthandProps[property]
         .map(function (p) {
             var longhand = p.substr(0, 1) === '-' ? property + p : p;
             return recurse ? expand(longhand, recurse) : longhand;
@@ -57,7 +71,7 @@ function expandAsArray(property, recurse) {
  */
 function expandAsObject(property, value, recurse) {
     var res = {};
-    if (!props.hasOwnProperty(property)) {
+    if (!shorthandProps.hasOwnProperty(property)) {
         res[property] = value;
         return res;
     }
@@ -84,9 +98,37 @@ function expandAsObject(property, value, recurse) {
     return res;
 }
 
+function compact(longhand) {
+    if (longhand.length) return compactProperties(longhand)
+}
+
+/**
+ * compactProperties — returns shorthand property from array of longhands.
+ *
+ * @param string[] props — longhand props
+ * @returns string — shorthand property
+ */
+function compactProperties(props) {
+    if (!isCompactable(props)) throw new Error(erros.propsArentCompactable);
+    return invertedShorthandProps[props[0]];
+}
+
 function isShorthand(property) {
-    if (props.hasOwnProperty(property)) {
+    if (shorthandProps.hasOwnProperty(property)) {
         return true;
     }
     return false;
 }
+
+/**
+ * isCompactable — check if array of longhands could be compacted
+ *
+ * @param string[] longhands — longhand props
+ * @returns Boolean
+ */
+function isCompactable(longhands) {
+    return longhands.every(function(prop) {
+        return invertedShorthandProps.hasOwnProperty(prop) &&
+            invertedShorthandProps[prop] === invertedShorthandProps[longhands[0]];
+    });
+}

test/04.compact-object.js

@@ -0,0 +1,10 @@
+describe('compact object', function () {
+    it('should compact an Array of props', function () {
+        SC.compact([
+            'border-top-left-radius',
+            'border-top-right-radius',
+            'border-bottom-right-radius',
+            'border-bottom-left-radius'
+        ]).should.eql('border-radius');
+    });
+});