Introduce even more modern JavaScript features in the code-base

After PR 12563 we're now free to use e.g. logical OR assignment, nullish coalescing, and optional chaining in the entire code-base.

src/core/ccitt.js

@@ -477,11 +477,7 @@ class CCITTFaxDecoder {
     this.byteAlign = options.EncodedByteAlign || false;
     this.columns = options.Columns || 1728;
     this.rows = options.Rows || 0;
-    let eoblock = options.EndOfBlock;
-    if (eoblock === null || eoblock === undefined) {
-      eoblock = true;
-    }
-    this.eoblock = eoblock;
+    this.eoblock = options.EndOfBlock ?? true;
     this.black = options.BlackIs1 || false;
 
     this.codingLine = new Uint32Array(this.columns + 1);

src/core/colorspace.js

@@ -928,8 +928,8 @@ const CalGrayCS = (function CalGrayCSClosure() {
           "WhitePoint missing - required for color space CalGray"
         );
       }
-      blackPoint = blackPoint || [0, 0, 0];
-      gamma = gamma || 1;
+      blackPoint ||= [0, 0, 0];
+      gamma ||= 1;
 
       // Translate arguments to spec variables.
       this.XW = whitePoint[0];

src/core/document.js

@@ -1702,7 +1702,7 @@ class PDFDocument {
 
   get calculationOrderIds() {
     const acroForm = this.catalog.acroForm;
-    if (!acroForm || !acroForm.has("CO")) {
+    if (!acroForm?.has("CO")) {
       return shadow(this, "calculationOrderIds", null);
     }
 

src/core/fonts.js

@@ -2579,7 +2579,7 @@ class Font {
     if (!isTrueType) {
       const isComposite =
         properties.composite &&
-        ((properties.cidToGidMap || []).length > 0 ||
+        (properties.cidToGidMap?.length > 0 ||
           !(properties.cMap instanceof IdentityCMap));
       // OpenType font (skip composite fonts with non-default glyph mapping).
       if (

src/core/xfa/formcalc_parser.js

@@ -1282,7 +1282,7 @@ class Parser {
     tok = tok2 || this.lexer.next();
     if (tok.id === TOKEN.step) {
       [tok, step] = this.parseSimpleExpr();
-      tok = tok || this.lexer.next();
+      tok ||= this.lexer.next();
     }
 
     if (tok.id !== TOKEN.do) {

src/core/xfa/template.js

@@ -932,7 +932,7 @@ class Border extends XFAObject {
     const { edges } = this[$getExtra]();
     const edgeStyles = edges.map(node => {
       const style = node[$toStyle]();
-      style.color = style.color || "#000000";
+      style.color ||= "#000000";
       return style;
     });
 
@@ -3871,7 +3871,7 @@ class NumericEdit extends XFAObject {
       attributes: {
         type: "text",
         fieldId: field[$uid],
-        dataId: (field[$data] && field[$data][$uid]) || field[$uid],
+        dataId: field[$data]?.[$uid] || field[$uid],
         class: ["xfaTextfield"],
         style,
         "aria-label": ariaLabel(field),

src/display/canvas.js

@@ -2061,7 +2061,7 @@ class CanvasGraphics {
     }
 
     if (isAddToPathSet) {
-      const paths = this.pendingTextPaths || (this.pendingTextPaths = []);
+      const paths = (this.pendingTextPaths ||= []);
       paths.push({
         transform: getCurrentTransform(ctx),
         x,

src/display/display_utils.js

@@ -760,22 +760,20 @@ class PDFDateString {
     }
 
     // Lazily initialize the regular expression.
-    if (!pdfDateStringRegex) {
-      pdfDateStringRegex = new RegExp(
-        "^D:" + // Prefix (required)
-          "(\\d{4})" + // Year (required)
-          "(\\d{2})?" + // Month (optional)
-          "(\\d{2})?" + // Day (optional)
-          "(\\d{2})?" + // Hour (optional)
-          "(\\d{2})?" + // Minute (optional)
-          "(\\d{2})?" + // Second (optional)
-          "([Z|+|-])?" + // Universal time relation (optional)
-          "(\\d{2})?" + // Offset hour (optional)
-          "'?" + // Splitting apostrophe (optional)
-          "(\\d{2})?" + // Offset minute (optional)
-          "'?" // Trailing apostrophe (optional)
-      );
-    }
+    pdfDateStringRegex ||= new RegExp(
+      "^D:" + // Prefix (required)
+        "(\\d{4})" + // Year (required)
+        "(\\d{2})?" + // Month (optional)
+        "(\\d{2})?" + // Day (optional)
+        "(\\d{2})?" + // Hour (optional)
+        "(\\d{2})?" + // Minute (optional)
+        "(\\d{2})?" + // Second (optional)
+        "([Z|+|-])?" + // Universal time relation (optional)
+        "(\\d{2})?" + // Offset hour (optional)
+        "'?" + // Splitting apostrophe (optional)
+        "(\\d{2})?" + // Offset minute (optional)
+        "'?" // Trailing apostrophe (optional)
+    );
 
     // Optional fields that don't satisfy the requirements from the regular
     // expression (such as incorrect digit counts or numbers that are out of

src/scripting_api/field.js

@@ -371,7 +371,7 @@ class Field extends PDFObject {
       nIdx = Array.isArray(this._currentValueIndices)
         ? this._currentValueIndices[0]
         : this._currentValueIndices;
-      nIdx = nIdx || 0;
+      nIdx ||= 0;
     }
 
     if (nIdx < 0 || nIdx >= this.numItems) {

web/chromecom.js

@@ -373,7 +373,7 @@ class ChromePreferences extends BasePreferences {
         );
 
         chrome.storage.managed.get(defaultManagedPrefs, function (items) {
-          items = items || defaultManagedPrefs;
+          items ||= defaultManagedPrefs;
           // Migration logic for deprecated preferences: If the new preference
           // is not defined by an administrator (i.e. the value is the same as
           // the default value), and a deprecated preference is set with a