add: cut out trimming text logic for md note title and add unit test

browser/lib/markdownTextHelper.js

@@ -0,0 +1,39 @@
+/**
+ * @fileoverview Text trimmer for markdown note.
+ */
+
+/**
+ * @param {string} input
+ * @return {string}
+ */
+export function strip (input) {
+  var output = input
+  try {
+    output = output
+      .replace(/^([\s\t]*)([\*\-\+]|\d+\.)\s+/gm, '$1')
+      .replace(/\n={2,}/g, '\n')
+      .replace(/~~/g, '')
+      .replace(/`{3}.*\n/g, '')
+      .replace(/<(.*?)>/g, '$1')
+      .replace(/^[=\-]{2,}\s*$/g, '')
+      .replace(/\[\^.+?\](: .*?$)?/g, '')
+      .replace(/\s{0,2}\[.*?\]: .*?$/g, '')
+      .replace(/!\[.*?\][\[\(].*?[\]\)]/g, '')
+      .replace(/\[(.*?)\][\[\(].*?[\]\)]/g, '$1')
+      .replace(/>/g, '')
+      .replace(/^\s{1,2}\[(.*?)\]: (\S+)( ".*?")?\s*$/g, '')
+      .replace(/^#{1,6}\s*([^#]*)\s*(#{1,6})?/gm, '$1')
+      .replace(/(`{3,})(.*?)\1/gm, '$2')
+      .replace(/^-{3,}\s*$/g, '')
+      .replace(/`(.+?)`/g, '$1')
+      .replace(/\n{2,}/g, '\n\n')
+  } catch (e) {
+    console.error(e)
+    return input
+  }
+  return output
+}
+
+export default {
+  strip,
+}