add new option namedCodesToUnicode (#236) (#253)

* add new option namedCodesToUnicode (#236)

* removed empty line from compiler constructor

README.md

@@ -16,6 +16,7 @@ The most lightweight, customizable React markdown component.
         - [options.overrides - Rendering Arbitrary React Components](#optionsoverrides---rendering-arbitrary-react-components)
         - [options.createElement - Custom React.createElement behavior](#optionscreateelement---custom-reactcreateelement-behavior)
         - [options.slugify](#optionsslugify)
+        - [options.namedCodesToUnicode](#optionsnamedcodestounicode)
     - [Getting the smallest possible bundle size](#getting-the-smallest-possible-bundle-size)
     - [Usage with Preact](#usage-with-preact)
 - [Gotchas](#gotchas)
@@ -358,6 +359,37 @@ compiler('# 中文', { slugify: str => str });
 <h1 id="中文">中文</h1>
 ```
 
+#### options.namedCodesToUnicode
+
+By default only a couple of named html codes are converted to unicode characters:
+
+* `&` (`&amp;`)
+* `'` (`&apos;`)
+* `>` (`&gt;`)
+* `<` (`&lt;`)
+* ` ` (`&nbsp;`)
+* `"` (`&quot;`)
+
+Some projects require to extend this map of named codes and unicode characters. To customize this list with additional html codes pass the option namedCodesToUnicode as object with the code names needed as in the example below:
+
+```jsx
+<Markdown options={{ namedCodesToUnicode: {
+    le: '\u2264',
+    ge: '\u2265',
+} }}>This text is &le; than this text.</Markdown>;
+
+// or
+
+compiler('This text is &le; than this text.', namedCodesToUnicode: {
+    le: '\u2264',
+    ge: '\u2265',
+});
+
+// renders:
+
+<p>This text is ≤ than this text.</p>
+```
+
 ### Getting the smallest possible bundle size
 
 Many development conveniences are placed behind `process.env.NODE_ENV !== "production"` conditionals. When bundling your app, it's a good idea to replace these code snippets such that a minifier (like uglify) can sweep them away and leave a smaller overall bundle.

index.js

@@ -716,6 +716,9 @@ export function compiler(markdown, options) {
   options = options || {};
   options.overrides = options.overrides || {};
   options.slugify = options.slugify || slugify;
+  options.namedCodesToUnicode = options.namedCodesToUnicode 
+    ? {...namedCodesToUnicode, ...options.namedCodesToUnicode}
+    : namedCodesToUnicode;
 
   const createElementFn = options.createElement || React.createElement;
 
@@ -1420,8 +1423,8 @@ export function compiler(markdown, options) {
           content: capture[0]
             // nbsp -> unicode equivalent for named chars
             .replace(HTML_CHAR_CODE_R, (full, inner) => {
-              return namedCodesToUnicode[inner]
-                ? namedCodesToUnicode[inner]
+              return options.namedCodesToUnicode[inner]
+                ? options.namedCodesToUnicode[inner]
                 : full;
             }),
         };