Adding documentation to charset_range.js

src/js/parser/javascript/charset_range.js

@@ -1,9 +1,13 @@
+// CharsetRange nodes are used for `[a-z]` regular expression syntax. The two
+// literal or escape nodes are rendered with a hyphen between them.
+
 import util from '../../util.js';
 import _ from 'lodash';
 
 export default {
   type: 'charset-range',
 
+  // Renders the charset range into the currently set container
   _render() {
     var contents = [
       this.first,
@@ -11,11 +15,13 @@ export default {
       this.last
     ];
 
+    // Render the nodes of the range.
     return Promise.all([
       this.first.render(this.container.group()),
       this.last.render(this.container.group())
     ])
       .then(() => {
+        // Space the nodes and hyphen horizontally.
         util.spaceHorizontally(contents, {
           padding: 5
         });
@@ -23,9 +29,12 @@ export default {
   },
 
   setup() {
+    // The two nodes for the range. In `[a-z]` these would be
+    // [Literal](./literal.html) nodes for "a" and "z".
     this.first = this.properties.first;
     this.last = this.properties.last;
 
+    // Report invalid expression when extents of the range are out of order.
     if (this.first.ordinal > this.last.ordinal) {
       throw `Range out of order in character class: ${this.textValue}`;
     }