Rollup merge of #97462 - GuillaumeGomez:more-eslint-rules, r=notriddle

Add more eslint rules

The last one is the most useful of this batch. :)

Here are the links for the eslint rules:

 * [arrow-parens](https://eslint.org/docs/rules/arrow-parens)
 * [no-unused-vars](https://eslint.org/docs/rules/no-unused-vars)
 * [eqeqeq](https://eslint.org/docs/rules/eqeqeq)

r? `@notriddle`

src/librustdoc/html/static/.eslintrc.js

@@ -54,5 +54,14 @@ module.exports = {
         "comma-style": ["error", "last"],
         "max-len": ["error", { "code": 100, "tabWidth": 4 }],
         "eol-last": ["error", "always"],
+        "arrow-parens": ["error", "as-needed"],
+        "no-unused-vars": [
+            "error",
+            {
+                "argsIgnorePattern": "^_",
+                "varsIgnorePattern": "^_"
+            }
+        ],
+        "eqeqeq": "error",
     }
 };

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

@@ -97,12 +97,12 @@ function showMain() {
 //
 // So I guess you could say things are getting pretty interoperable.
 function getVirtualKey(ev) {
-    if ("key" in ev && typeof ev.key != "undefined") {
+    if ("key" in ev && typeof ev.key !== "undefined") {
         return ev.key;
     }
 
     const c = ev.charCode || ev.keyCode;
-    if (c == 27) {
+    if (c === 27) {
         return "Escape";
     }
     return String.fromCharCode(c);

src/librustdoc/html/static/js/search.js

@@ -70,7 +70,7 @@ function printTab(nb) {
     });
     if (foundCurrentTab && foundCurrentResultSet) {
         searchState.currentTab = nb;
-    } else if (nb != 0) {
+    } else if (nb !== 0) {
         printTab(0);
     }
 }
@@ -200,7 +200,7 @@ function initSearch(rawSearchIndex) {
      * @return {boolean}
      */
     function isPathStart(parserState) {
-        return parserState.userQuery.slice(parserState.pos, parserState.pos + 2) == "::";
+        return parserState.userQuery.slice(parserState.pos, parserState.pos + 2) === "::";
     }
 
     /**
@@ -211,7 +211,7 @@ function initSearch(rawSearchIndex) {
      * @return {boolean}
      */
     function isReturnArrow(parserState) {
-        return parserState.userQuery.slice(parserState.pos, parserState.pos + 2) == "->";
+        return parserState.userQuery.slice(parserState.pos, parserState.pos + 2) === "->";
     }
 
     /**
@@ -1726,7 +1726,7 @@ function initSearch(rawSearchIndex) {
             crates = " in <select id=\"crate-search\"><option value=\"All crates\">" +
                 "All crates</option>";
             for (const c of window.ALL_CRATES) {
-                crates += `<option value="${c}" ${c == filterCrates && "selected"}>${c}</option>`;
+                crates += `<option value="${c}" ${c === filterCrates && "selected"}>${c}</option>`;
             }
             crates += "</select>";
         }