docs: replace var with const in rule examples (eslint#19299)

* docs: replace var with const in rule example

* revert changes in no-else-block

* replace var in no-empty-pattern

docs/src/rules/no-dupe-class-members.md

@@ -15,7 +15,7 @@ class Foo {
   bar() { console.log("goodbye"); }
 }
 
-var foo = new Foo();
+const foo = new Foo();
 foo.bar(); // goodbye
 ```
 

docs/src/rules/no-dupe-keys.md

@@ -9,7 +9,7 @@ handled_by_typescript: true
 Multiple properties with the same key in object literals can cause unexpected behavior in your application.
 
 ```js
-var foo = {
+const foo = {
     bar: "baz",
     bar: "qux"
 };
@@ -26,17 +26,17 @@ Examples of **incorrect** code for this rule:
 ```js
 /*eslint no-dupe-keys: "error"*/
 
-var foo = {
+const foo = {
     bar: "baz",
     bar: "qux"
 };
 
-var foo = {
+const bar = {
     "bar": "baz",
     bar: "qux"
 };
 
-var foo = {
+const baz = {
     0x1: "baz",
     1: "qux"
 };
@@ -51,7 +51,7 @@ Examples of **correct** code for this rule:
 ```js
 /*eslint no-dupe-keys: "error"*/
 
-var foo = {
+const foo = {
     bar: "baz",
     quxx: "qux"
 };

docs/src/rules/no-duplicate-case.md

@@ -18,7 +18,7 @@ Examples of **incorrect** code for this rule:
 ```js
 /*eslint no-duplicate-case: "error"*/
 
-var a = 1,
+const a = 1,
     one = 1;
 
 switch (a) {
@@ -64,7 +64,7 @@ Examples of **correct** code for this rule:
 ```js
 /*eslint no-duplicate-case: "error"*/
 
-var a = 1,
+const a = 1,
     one = 1;
 
 switch (a) {

docs/src/rules/no-empty-character-class.md

@@ -8,7 +8,7 @@ rule_type: problem
 Because empty character classes in regular expressions do not match anything, they might be typing mistakes.
 
 ```js
-var foo = /^abc[]/;
+const foo = /^abc[]/;
 ```
 
 ## Rule Details
@@ -73,5 +73,5 @@ Example of a *false negative* when this rule reports correct code:
 ```js
 /*eslint no-empty-character-class: "error"*/
 
-var abcNeverMatches = new RegExp("^abc[]");
+const abcNeverMatches = new RegExp("^abc[]");
 ```

docs/src/rules/no-empty-pattern.md

@@ -9,21 +9,21 @@ When using destructuring, it's possible to create a pattern that has no effect.
 
 ```js
 // doesn't create any variables
-var {a: {}} = foo;
+const {a: {}} = foo;
 ```
 
 In this code, no new variables are created because `a` is just a location helper while the `{}` is expected to contain the variables to create, such as:
 
 ```js
 // creates variable b
-var {a: { b }} = foo;
+const {a: { b }} = foo;
 ```
 
 In many cases, the empty object pattern is a mistake where the author intended to use a default value instead, such as:
 
 ```js
 // creates variable a
-var {a = {}} = foo;
+const {a = {}} = foo;
 ```
 
 The difference between these two patterns is subtle, especially because the problematic empty pattern looks just like an object literal.
@@ -39,10 +39,10 @@ Examples of **incorrect** code for this rule:
 ```js
 /*eslint no-empty-pattern: "error"*/
 
-var {} = foo;
-var [] = foo;
-var {a: {}} = foo;
-var {a: []} = foo;
+const {} = foo;
+const [] = foo;
+const {a: {}} = foo;
+const {a: []} = foo;
 function foo({}) {}
 function bar([]) {}
 function baz({a: {}}) {}
@@ -58,8 +58,8 @@ Examples of **correct** code for this rule:
 ```js
 /*eslint no-empty-pattern: "error"*/
 
-var {a = {}} = foo;
-var {a = []} = foo;
+const {a = {}} = foo;
+const {b = []} = foo;
 function foo({a = {}}) {}
 function bar({a = []}) {}
 ```
@@ -84,10 +84,10 @@ Examples of **incorrect** code for this rule with the `{"allowObjectPatternsAsPa
 /*eslint no-empty-pattern: ["error", { "allowObjectPatternsAsParameters": true }]*/
 
 function foo({a: {}}) {}
-var bar = function({a: {}}) {};
-var bar = ({a: {}}) => {};
-var bar = ({} = bar) => {};
-var bar = ({} = { bar: 1 }) => {};
+const bar = function({a: {}}) {};
+const qux = ({a: {}}) => {};
+const quux = ({} = bar) => {};
+const item = ({} = { bar: 1 }) => {};
 
 function baz([]) {}
 ```
@@ -102,8 +102,8 @@ Examples of **correct** code for this rule with the `{"allowObjectPatternsAsPara
 /*eslint no-empty-pattern: ["error", { "allowObjectPatternsAsParameters": true }]*/
 
 function foo({}) {}
-var bar = function({}) {};
-var bar = ({}) => {};
+const bar = function({}) {};
+const qux = ({}) => {};
 
 function baz({} = {}) {}
 ```