Introduce some functional programming techniques

src/file/table-of-contents/table-of-contents-properties.ts

@@ -1,6 +1,6 @@
 export class StyleLevel {
-    public styleName: string;
-    public level: number;
+    public readonly styleName: string;
+    public readonly level: number;
 
     constructor(styleName: string, level: number) {
         this.styleName = styleName;
@@ -22,13 +22,13 @@ export interface ITableOfContentsOptions {
      * The identifier designated by text in this switch's field-argument corresponds to the caption label.
      * Use captionLabelIncludingNumbers (\c) to build a table of captions with labels and numbers.
      */
-    captionLabel?: string;
+    readonly captionLabel?: string;
 
     /**
      * \b option - Includes entries only from the portion of the document marked by
      * the bookmark named by text in this switch's field-argument.
      */
-    entriesFromBookmark?: string;
+    readonly entriesFromBookmark?: string;
 
     /**
      * \c option -  Includes figures, tables, charts, and other items that are numbered
@@ -36,24 +36,24 @@ export interface ITableOfContentsOptions {
      * field-argument, which corresponds to the caption label, shall match the identifier in the
      * corresponding SEQ field.
      */
-    captionLabelIncludingNumbers?: string;
+    readonly captionLabelIncludingNumbers?: string;
 
     /**
      * \d option - When used with \s, the text in this switch's field-argument defines
      * the separator between sequence and page numbers. The default separator is a hyphen (-).
      */
-    sequenceAndPageNumbersSeparator?: string;
+    readonly sequenceAndPageNumbersSeparator?: string;
 
     /**
      * \f option - Includes only those TC fields whose identifier exactly matches the
      * text in this switch's field-argument (which is typically a letter).
      */
-    tcFieldIdentifier?: string;
+    readonly tcFieldIdentifier?: string;
 
     /**
      * \h option - Makes the table of contents entries hyperlinks.
      */
-    hyperlink?: boolean;
+    readonly hyperlink?: boolean;
 
     /**
      * \l option - Includes TC fields that assign entries to one of the levels specified
@@ -61,14 +61,14 @@ export interface ITableOfContentsOptions {
      * where startLevel and endLevel are integers, and startLevel has a value equal-to or less-than endLevel.
      * TC fields that assign entries to lower levels are skipped.
      */
-    tcFieldLevelRange?: string;
+    readonly tcFieldLevelRange?: string;
 
     /**
      * \n option - Without field-argument, omits page numbers from the table of contents.
      * Page numbers are omitted from all levels unless a range of entry levels is specified by
      * text in this switch's field-argument. A range is specified as for \l.
      */
-    pageNumbersEntryLevelsRange?: string;
+    readonly pageNumbersEntryLevelsRange?: string;
 
     /**
      * \o option -  Uses paragraphs formatted with all or the specified range of builtin
@@ -77,20 +77,20 @@ export interface ITableOfContentsOptions {
      * to the style with a style ID of HeadingX (e.g. 1 corresponds to Heading1).
      * If no heading range is specified, all heading levels used in the document are listed.
      */
-    headingStyleRange?: string;
+    readonly headingStyleRange?: string;
 
     /**
      * \p option - Text in this switch's field-argument specifies a sequence of characters
      * that separate an entry and its page number. The default is a tab with leader dots.
      */
-    entryAndPageNumberSeparator?: string;
+    readonly entryAndPageNumberSeparator?: string;
 
     /**
      * \s option - For entries numbered with a SEQ field (§17.16.5.56), adds a prefix to the page number.
      * The prefix depends on the type of entry. text in this switch's field-argument shall match the
      * identifier in the SEQ field.
      */
-    seqFieldIdentifierForPrefix?: string;
+    readonly seqFieldIdentifierForPrefix?: string;
 
     /**
      * \t field-argument Uses paragraphs formatted with styles other than the built-in heading styles.
@@ -98,25 +98,25 @@ export interface ITableOfContentsOptions {
      * with each doublet being a comma-separated set of style name and table of content level.
      * \t can be combined with \o.
      */
-    stylesWithLevels?: StyleLevel[];
+    readonly stylesWithLevels?: StyleLevel[];
 
     /**
      * \u Uses the applied paragraph outline level.
      */
-    useAppliedParagraphOutlineLevel?: boolean;
+    readonly useAppliedParagraphOutlineLevel?: boolean;
 
     /**
      * \w Preserves tab entries within table entries.
      */
-    preserveTabInEntries?: boolean;
+    readonly preserveTabInEntries?: boolean;
 
     /**
      * \x Preserves newline characters within table entries.
      */
-    preserveNewLineInEntries?: boolean;
+    readonly preserveNewLineInEntries?: boolean;
 
     /**
      * \z Hides tab leader and page numbers in web page view (§17.18.102).
      */
-    hideTabAndPageNumbersInWebView?: boolean;
+    readonly hideTabAndPageNumbersInWebView?: boolean;
 }