JavaScript: avoid assignment in if

Author: simon04

assets/javascripts/app/db.js

@@ -150,8 +150,8 @@ app.DB = class DB {
   }
 
   onUpgradeNeeded(event) {
-    let db;
-    if (!(db = event.target.result)) {
+    const db = event.target.result;
+    if (!db) {
       return;
     }
 
@@ -351,7 +351,7 @@ app.DB = class DB {
   load(entry, onSuccess, onError) {
     if (this.shouldLoadWithIDB(entry)) {
       return this.loadWithIDB(entry, onSuccess, () =>
-        this.loadWithXHR(entry, onSuccess, onError),
+        this.loadWithXHR(entry, onSuccess, onError)
       );
     } else {
       return this.loadWithXHR(entry, onSuccess, onError);
@@ -418,8 +418,8 @@ app.DB = class DB {
 
     const req = txn.objectStore("docs").openCursor();
     req.onsuccess = (event) => {
-      let cursor;
-      if (!(cursor = event.target.result)) {
+      const cursor = event.target.result;
+      if (!cursor) {
         return;
       }
       this.cachedDocs[cursor.key] = cursor.value;

assets/javascripts/app/router.js

@@ -35,12 +35,12 @@ app.Router = class Router extends Events {
   }
 
   before(context, next) {
-    let res;
     const previousContext = this.context;
     this.context = context;
     this.trigger("before", context);
 
-    if ((res = next())) {
+    const res = next();
+    if (res) {
       this.context = previousContext;
       return res;
     } else {
@@ -79,27 +79,29 @@ app.Router = class Router extends Events {
   }
 
   entry(context, next) {
-    let entry;
     const doc = app.docs.findBySlug(context.params.doc);
     if (!doc) {
       return next();
     }
     let { path } = context.params;
     const { hash } = context;
 
-    if ((entry = doc.findEntryByPathAndHash(path, hash))) {
+    let entry = doc.findEntryByPathAndHash(path, hash);
+    if (entry) {
       context.doc = doc;
       context.entry = entry;
       this.triggerRoute("entry");
       return;
     } else if (path.slice(-6) === "/index") {
       path = path.substr(0, path.length - 6);
-      if ((entry = doc.findEntryByPathAndHash(path, hash))) {
+      entry = doc.findEntryByPathAndHash(path, hash);
+      if (entry) {
         return entry.fullPath();
       }
     } else {
       path = `${path}/index`;
-      if ((entry = doc.findEntryByPathAndHash(path, hash))) {
+      entry = doc.findEntryByPathAndHash(path, hash);
+      if (entry) {
         return entry.fullPath();
       }
     }
@@ -169,10 +171,8 @@ app.Router = class Router extends Events {
 
   setInitialPath() {
     // Remove superfluous forward slashes at the beginning of the path
-    let path;
-    if (
-      (path = location.pathname.replace(/^\/{2,}/g, "/")) !== location.pathname
-    ) {
+    let path = location.pathname.replace(/^\/{2,}/g, "/");
+    if (path !== location.pathname) {
       page.replace(path + location.search + location.hash, null, true);
     }
 
@@ -192,8 +192,8 @@ app.Router = class Router extends Events {
   }
 
   getInitialPathFromCookie() {
-    let path;
-    if ((path = Cookies.get("initial_path"))) {
+    const path = Cookies.get("initial_path");
+    if (path) {
       Cookies.expire("initial_path");
       return path;
     }
@@ -203,7 +203,7 @@ app.Router = class Router extends Events {
     page.replace(
       location.pathname + location.search + (hash || ""),
       null,
-      true,
+      true
     );
   }
 };

assets/javascripts/lib/ajax.js

@@ -101,8 +101,8 @@ function ajax(options) {
 
   function onComplete(xhr, options) {
     if (200 <= xhr.status && xhr.status < 300) {
-      let response;
-      if ((response = parseResponse(xhr, options)) != null) {
+      const response = parseResponse(xhr, options);
+      if (response != null) {
         onSuccess(response, xhr, options);
       } else {
         onError("invalid", xhr, options);

assets/javascripts/lib/page.js

@@ -42,14 +42,14 @@ page.stop = function () {
 };
 
 page.show = function (path, state) {
-  let res;
   if (path === currentState?.path) {
     return;
   }
   const context = new Context(path, state);
   const previousState = currentState;
   currentState = context.state;
-  if ((res = page.dispatch(context))) {
+  const res = page.dispatch(context);
+  if (res) {
     currentState = previousState;
     location.assign(res);
   } else {
@@ -84,12 +84,9 @@ page.replace = function (path, state, skipDispatch, init) {
 
 page.dispatch = function (context) {
   let i = 0;
-  var next = function () {
-    let fn, res;
-    if ((fn = callbacks[i++])) {
-      res = fn(context, next);
-    }
-    return res;
+  const next = function () {
+    let fn = callbacks[i++];
+    return fn?.(context, next);
   };
   return next();
 };
@@ -170,8 +167,8 @@ class Route {
 
   middleware(fn) {
     return (context, next) => {
-      let params;
-      if (this.match(context.pathname, (params = []))) {
+      let params = [];
+      if (this.match(context.pathname, params)) {
         context.params = params;
         return fn(context, next);
       } else {
@@ -181,19 +178,19 @@ class Route {
   }
 
   match(path, params) {
-    let matchData;
-    if (!(matchData = this.regexp.exec(path))) {
+    const matchData = this.regexp.exec(path);
+    if (!matchData) {
       return;
     }
 
     const iterable = matchData.slice(1);
     for (let i = 0; i < iterable.length; i++) {
-      var key;
+      var key = this.keys[i];
       var value = iterable[i];
       if (typeof value === "string") {
         value = decodeURIComponent(value);
       }
-      if ((key = this.keys[i])) {
+      if (key) {
         params[key.name] = value;
       } else {
         params.push(value);

assets/javascripts/lib/util.js

@@ -340,8 +340,8 @@ $.scrollToWithImageLock = function (el, parent, ...args) {
 
 // Calls the function while locking the element's position relative to the window.
 $.lockScroll = function (el, fn) {
-  let parent;
-  if ((parent = $.scrollParent(el))) {
+  const parent = $.scrollParent(el);
+  if (parent) {
     let { top } = $.rect(el);
     if (![document.body, document.documentElement].includes(parent)) {
       top -= $.rect(parent).top;

assets/javascripts/models/doc.js

@@ -72,8 +72,8 @@ app.models.Doc = class Doc extends app.Model {
   }
 
   findEntryByPathAndHash(path, hash) {
-    let entry;
-    if (hash && (entry = this.entries.findBy("path", `${path}#${hash}`))) {
+    const entry = hash && this.entries.findBy("path", `${path}#${hash}`);
+    if (entry) {
       return entry;
     } else if (path === "index") {
       return this.toEntry();
@@ -110,8 +110,8 @@ app.models.Doc = class Doc extends app.Model {
   }
 
   _loadFromCache(onSuccess) {
-    let data;
-    if (!(data = this._getCache())) {
+    const data = this._getCache();
+    if (!data) {
       return;
     }
 
@@ -125,8 +125,8 @@ app.models.Doc = class Doc extends app.Model {
   }
 
   _getCache() {
-    let data;
-    if (!(data = app.localStorage.get(this.slug))) {
+    const data = app.localStorage.get(this.slug);
+    if (!data) {
       return;
     }
 

assets/javascripts/views/content/offline_page.js

@@ -68,17 +68,17 @@ app.views.OfflinePage = class OfflinePage extends app.View {
   }
 
   onClick(event) {
-    let action;
     let el = $.eventTarget(event);
-    if ((action = el.getAttribute("data-action"))) {
+    let action = el.getAttribute("data-action");
+    if (action) {
       const doc = this.docByEl(el);
       if (action === "update") {
         action = "install";
       }
       doc[action](
         this.onInstallSuccess.bind(this, doc),
         this.onInstallError.bind(this, doc),
-        this.onInstallProgress.bind(this, doc),
+        this.onInstallProgress.bind(this, doc)
       );
       el.parentNode.innerHTML = `${el.textContent.replace(/e$/, "")}ing…`;
     } else if (
@@ -101,11 +101,11 @@ app.views.OfflinePage = class OfflinePage extends app.View {
       return;
     }
     doc.getInstallStatus((status) => {
-      let el;
       if (!this.activated) {
         return;
       }
-      if ((el = this.docEl(doc))) {
+      const el = this.docEl(doc);
+      if (el) {
         el.outerHTML = this.renderDoc(doc, status);
         $.highlight(el, { className: "_highlight" });
         this.refreshLinks();
@@ -114,25 +114,25 @@ app.views.OfflinePage = class OfflinePage extends app.View {
   }
 
   onInstallError(doc) {
-    let el;
     if (!this.activated) {
       return;
     }
-    if ((el = this.docEl(doc))) {
+    const el = this.docEl(doc);
+    if (el) {
       el.lastElementChild.textContent = "Error";
     }
   }
 
   onInstallProgress(doc, event) {
-    let el;
     if (!this.activated || !event.lengthComputable) {
       return;
     }
-    if ((el = this.docEl(doc))) {
+    const el = this.docEl(doc);
+    if (el) {
       const percentage = Math.round((event.loaded * 100) / event.total);
       el.lastElementChild.textContent = el.lastElementChild.textContent.replace(
         /(\s.+)?$/,
-        ` (${percentage}%)`,
+        ` (${percentage}%)`
       );
     }
   }

assets/javascripts/views/layout/mobile.js

@@ -76,7 +76,6 @@ app.views.Mobile = class Mobile extends app.View {
   }
 
   showSidebar() {
-    let selection;
     if (this.isSidebarShown()) {
       window.scrollTo(0, 0);
       return;
@@ -86,7 +85,8 @@ app.views.Mobile = class Mobile extends app.View {
     this.content.style.display = "none";
     this.sidebar.style.display = "block";
 
-    if ((selection = this.findByClass(app.views.ListSelect.activeClass))) {
+    const selection = this.findByClass(app.views.ListSelect.activeClass);
+    if (selection) {
       const scrollContainer =
         window.scrollY === this.body.scrollTop
           ? this.body

assets/javascripts/views/layout/path.js

@@ -24,8 +24,8 @@ app.views.Path = class Path extends app.View {
   }
 
   onClick(event) {
-    let link;
-    if ((link = $.closestLink(event.target, this.el))) {
+    const link = $.closestLink(event.target, this.el);
+    if (link) {
       this.clicked = true;
     }
   }