add hw2

node_modules/postcss-import/lib/join-media.js

@@ -0,0 +1,28 @@
+"use strict"
+
+const startsWithKeywordRegexp = /^(all|not|only|print|screen)/i
+
+module.exports = function (parentMedia, childMedia) {
+  if (!parentMedia.length && childMedia.length) return childMedia
+  if (parentMedia.length && !childMedia.length) return parentMedia
+  if (!parentMedia.length && !childMedia.length) return []
+
+  const media = []
+
+  parentMedia.forEach(parentItem => {
+    const parentItemStartsWithKeyword = startsWithKeywordRegexp.test(parentItem)
+
+    childMedia.forEach(childItem => {
+      const childItemStartsWithKeyword = startsWithKeywordRegexp.test(childItem)
+      if (parentItem !== childItem) {
+        if (childItemStartsWithKeyword && !parentItemStartsWithKeyword) {
+          media.push(`${childItem} and ${parentItem}`)
+        } else {
+          media.push(`${parentItem} and ${childItem}`)
+        }
+      }
+    })
+  })
+
+  return media
+}