Adding warnings for non-standard escape sequence usage

src/js/parser/javascript.js

@@ -9,7 +9,8 @@ export default class Parser {
       groupCounter: 1,
       renderCounter: 0,
       maxCounter: 0,
-      cancelRender: false
+      cancelRender: false,
+      warnings: []
     };
   }
 
@@ -58,4 +59,8 @@ export default class Parser {
   cancel() {
     this.state.cancelRender = true;
   }
+
+  get warnings() {
+    return this.state.warnings;
+  }
 }

src/js/parser/javascript/charset.js

@@ -41,5 +41,9 @@ export default {
     this.elements = _.unique(this.properties.parts.elements, part => {
       return [part.type, part.textValue].join(':');
     });
+
+    if (this.textValue.match(/\\c[^a-zA-Z]/)) {
+      this.state.warnings.push(`The character set "${this.textValue}" contains the \\c escape followed by a character other than A-Z. This can lead to different behavior depending on browser. The representation here is the most common interpretation.`);
+    }
   }
-};
+}