rustdoc: clean up JS

* Stop checking `func` in `onEach`. It's always hard-coded right
  at the call site, so there's no point.
* Use the ternary operator in a few spots where it makes sense.
* No point in making `onEach` store `arr.length` in a variable if
  it's only used once anyway.

Author: notriddle

src/librustdoc/html/static/js/main.js

@@ -332,13 +332,7 @@ function preLoadCss(cssUrl) {
     };
 
     function getPageId() {
-        if (window.location.hash) {
-            const tmp = window.location.hash.replace(/^#/, "");
-            if (tmp.length > 0) {
-                return tmp;
-            }
-        }
-        return null;
+        return window.location.hash.replace(/^#/, "");
     }
 
     const toggleAllDocsId = "toggle-all-docs";
@@ -707,7 +701,7 @@ function preLoadCss(cssUrl) {
         });
 
         const pageId = getPageId();
-        if (pageId !== null) {
+        if (pageId !== "") {
             expandSection(pageId);
         }
     }());

src/librustdoc/html/static/js/settings.js

@@ -86,12 +86,8 @@
             if (settingId === "theme") {
                 const useSystem = getSettingValue("use-system-theme");
                 if (useSystem === "true" || settingValue === null) {
-                    if (useSystem !== "false") {
-                        settingValue = "system preference";
-                    } else {
-                        // This is the default theme.
-                        settingValue = "light";
-                    }
+                    // "light" is the default theme
+                    settingValue = useSystem === "false" ? "light" : "system preference";
                 }
             }
             if (settingValue !== null && settingValue !== "null") {

src/librustdoc/html/static/js/storage.js

@@ -53,10 +53,9 @@ function removeClass(elem, className) {
  * @param {boolean}     [reversed] - Whether to iterate in reverse
  */
 function onEach(arr, func, reversed) {
-    if (arr && arr.length > 0 && func) {
+    if (arr && arr.length > 0) {
         if (reversed) {
-            const length = arr.length;
-            for (let i = length - 1; i >= 0; --i) {
+            for (let i = arr.length - 1; i >= 0; --i) {
                 if (func(arr[i])) {
                     return true;
                 }
@@ -150,26 +149,18 @@ const updateTheme = (function() {
      * … dictates that it should be.
      */
     function updateTheme() {
-        const use = (theme, saveTheme) => {
-            switchTheme(theme, saveTheme);
-        };
-
         // maybe the user has disabled the setting in the meantime!
         if (getSettingValue("use-system-theme") !== "false") {
             const lightTheme = getSettingValue("preferred-light-theme") || "light";
             const darkTheme = getSettingValue("preferred-dark-theme") || "dark";
 
-            if (mql.matches) {
-                use(darkTheme, true);
-            } else {
-                // prefers a light theme, or has no preference
-                use(lightTheme, true);
-            }
+            // use light theme if user prefers it, or has no preference
+            switchTheme(mql.matches ? darkTheme : lightTheme, true);
             // note: we save the theme so that it doesn't suddenly change when
             // the user disables "use-system-theme" and reloads the page or
             // navigates to another page
         } else {
-            use(getSettingValue("theme"), false);
+            switchTheme(getSettingValue("theme"), false);
         }
     }