Escape double quotes according to RFC 4180 (#66)

Fixes #65

lib/__specs__/main.spec.ts

@@ -196,6 +196,44 @@ describe("ExportToCsv", () => {
     );
   });
 
+  it("should escape double quotes when quote is double quote", () => {
+    const options: ConfigOptions = {
+      quoteCharacter: '"',
+      filename: "Test Csv 2",
+      useBom: false,
+      showColumnHeaders: true,
+      useKeysAsHeaders: true,
+    };
+
+    const output = generateCsv(options)([
+      {
+        "escape-it": 24,
+        song: 'Mack "The Knife"',
+      },
+    ]);
+
+    expect(output).toBe('"escape-it","song"\r\n24,"Mack ""The Knife"""\r\n');
+  });
+
+  it("should not escape double quotes when quote is not double quote", () => {
+    const options: ConfigOptions = {
+      quoteCharacter: "'",
+      filename: "Test Csv 2",
+      useBom: false,
+      showColumnHeaders: true,
+      useKeysAsHeaders: true,
+    };
+
+    const output = generateCsv(options)([
+      {
+        "escape-it": 24,
+        song: 'Mack "The Knife"',
+      },
+    ]);
+
+    expect(output).toBe("'escape-it','song'\r\n24,'Mack \"The Knife\"'\r\n");
+  });
+
   it("should properly quote headers", () => {
     const options: ConfigOptions = {
       filename: "Test Csv 2",

lib/helpers.ts

@@ -133,10 +133,14 @@ export const formatData = (config: ConfigOptions, data: any): string => {
     if (
       config.quoteStrings ||
       (config.fieldSeparator && data.indexOf(config.fieldSeparator) > -1) ||
+      (config.quoteCharacter && data.indexOf(config.quoteCharacter) > -1) ||
       data.indexOf("\n") > -1 ||
       data.indexOf("\r") > -1
     ) {
-      val = config.quoteCharacter + data + config.quoteCharacter;
+      val =
+        config.quoteCharacter +
+        escapeDoubleQuotes(data, config.quoteCharacter) +
+        config.quoteCharacter;
     }
     return val;
   }
@@ -149,3 +153,17 @@ export const formatData = (config: ConfigOptions, data: any): string => {
   }
   return data;
 };
+
+/**
+ * If double-quotes are used to enclose fields, then a double-quote
+ * appearing inside a field must be escaped by preceding it with
+ * another double quote.
+ *
+ * See https://www.rfc-editor.org/rfc/rfc4180
+ */
+function escapeDoubleQuotes(data: string, quoteCharacter?: string): string {
+  if (quoteCharacter == '"' && data.indexOf('"') > -1) {
+    return data.replace(/"/g, '""');
+  }
+  return data;
+}