docs: replace var with const in examples (#19539)

* docs: replace var with const in examples

* docs: update examples no-shadow

Author: snitin315

Diff for: docs/src/rules/no-shadow-restricted-names.md

@@ -13,7 +13,7 @@ further_reading:
 ES5 §15.1.1 Value Properties of the Global Object (`NaN`, `Infinity`, `undefined`) as well as strict mode restricted identifiers `eval` and `arguments` are considered to be restricted names in JavaScript. Defining them to mean something else can have unintended consequences and confuse others reading the code. For example, there's nothing preventing you from writing:
 
 ```js
-var undefined = "foo";
+const undefined = "foo";
 ```
 
 Then any code used within the same scope would not get the global `undefined`, but rather the local version with a very different meaning.
@@ -31,7 +31,7 @@ function NaN(){}
 
 !function(Infinity){};
 
-var undefined = 5;
+const undefined = 5;
 
 try {} catch(eval){}
 ```
@@ -59,12 +59,12 @@ Examples of **correct** code for this rule:
 ```js
 /*eslint no-shadow-restricted-names: "error"*/
 
-var Object;
+let Object;
 
 function f(a, b){}
 
 // Exception: `undefined` may be shadowed if the variable is never assigned a value.
-var undefined;
+let undefined;
 ```
 
 :::

Diff for: docs/src/rules/no-shadow.md

@@ -11,9 +11,9 @@ further_reading:
 Shadowing is the process by which a local variable shares the same name as a variable in its containing scope. For example:
 
 ```js
-var a = 3;
+const a = 3;
 function b() {
-    var a = 10;
+    const a = 10;
 }
 ```
 
@@ -30,13 +30,13 @@ Examples of **incorrect** code for this rule:
 ```js
 /*eslint no-shadow: "error"*/
 
-var a = 3;
+const a = 3;
 function b() {
-    var a = 10;
+    const a = 10;
 }
 
-var c = function () {
-    var a = 10;
+const c = function () {
+    const a = 10;
 }
 
 function d(a) {
@@ -45,7 +45,7 @@ function d(a) {
 d(a);
 
 if (true) {
-    let a = 5;
+    const a = 5;
 }
 ```
 
@@ -74,7 +74,7 @@ Examples of **incorrect** code for the `{ "builtinGlobals": true }` option:
 /*eslint no-shadow: ["error", { "builtinGlobals": true }]*/
 
 function foo() {
-    var Object = 0;
+    const Object = 0;
 }
 ```
 
@@ -98,15 +98,15 @@ Examples of **incorrect** code for the default `{ "hoist": "functions" }` option
 /*eslint no-shadow: ["error", { "hoist": "functions" }]*/
 
 if (true) {
-    let b = 6;
+    const b = 6;
 }
 
 function b() {}
 ```
 
 :::
 
-Although `let b` in the `if` statement is before the *function* declaration in the outer scope, it is incorrect.
+Although `const b` in the `if` statement is before the *function* declaration in the outer scope, it is incorrect.
 
 Examples of **correct** code for the default `{ "hoist": "functions" }` option:
 
@@ -116,15 +116,15 @@ Examples of **correct** code for the default `{ "hoist": "functions" }` option:
 /*eslint no-shadow: ["error", { "hoist": "functions" }]*/
 
 if (true) {
-    let a = 3;
+    const a = 3;
 }
 
-let a = 5;
+const a = 5;
 ```
 
 :::
 
-Because `let a` in the `if` statement is before the *variable* declaration in the outer scope, it is correct.
+Because `const a` in the `if` statement is before the *variable* declaration in the outer scope, it is correct.
 
 #### hoist: all
 
@@ -136,11 +136,11 @@ Examples of **incorrect** code for the `{ "hoist": "all" }` option:
 /*eslint no-shadow: ["error", { "hoist": "all" }]*/
 
 if (true) {
-    let a = 3;
-    let b = 6;
+    const a = 3;
+    const b = 6;
 }
 
-let a = 5;
+const a = 5;
 function b() {}
 ```
 
@@ -156,17 +156,17 @@ Examples of **correct** code for the `{ "hoist": "never" }` option:
 /*eslint no-shadow: ["error", { "hoist": "never" }]*/
 
 if (true) {
-    let a = 3;
-    let b = 6;
+    const a = 3;
+    const b = 6;
 }
 
-let a = 5;
+const a = 5;
 function b() {}
 ```
 
 :::
 
-Because `let a` and `let b` in the `if` statement are before the declarations in the outer scope, they are correct.
+Because `const a` and `const b` in the `if` statement are before the declarations in the outer scope, they are correct.
 
 ### allow
 
@@ -207,7 +207,7 @@ Examples of **incorrect** code for the `{ "ignoreOnInitialization": "true" }` op
 ```js
 /*eslint no-shadow: ["error", { "ignoreOnInitialization": true }]*/
 
-var x = x => x;
+const x = x => x;
 ```
 
 :::
@@ -221,9 +221,9 @@ Examples of **correct** code for the `{ "ignoreOnInitialization": true }` option
 ```js
 /*eslint no-shadow: ["error", { "ignoreOnInitialization": true }]*/
 
-var x = foo(x => x)
+const x = foo(x => x)
 
-var y = (y => y)()
+const y = (y => y)()
 ```
 
 :::

Diff for: docs/src/rules/no-throw-literal.md

@@ -28,12 +28,12 @@ throw undefined;
 
 throw null;
 
-var err = new Error();
+const err = new Error();
 throw "an " + err;
 // err is recast to a string literal
 
-var err = new Error();
-throw `${err}`
+const er2 = new Error();
+throw `${err2}`
 
 ```
 
@@ -50,7 +50,7 @@ throw new Error();
 
 throw new Error("error");
 
-var e = new Error("error");
+const e = new Error("error");
 throw e;
 
 try {
@@ -73,7 +73,7 @@ Examples of **correct** code for this rule, but which do not throw an `Error` ob
 ```js
 /*eslint no-throw-literal: "error"*/
 
-var err = "error";
+const err = "error";
 throw err;
 
 function foo(bar) {
@@ -83,7 +83,7 @@ throw foo("error");
 
 throw new String("error");
 
-var baz = {
+const baz = {
     bar: "error"
 };
 throw baz.bar;

Diff for: docs/src/rules/no-underscore-dangle.md

@@ -6,7 +6,7 @@ rule_type: suggestion
 As far as naming conventions for identifiers go, dangling underscores may be the most polarizing in JavaScript. Dangling underscores are underscores at either the beginning or end of an identifier, such as:
 
 ```js
-var _foo;
+let _foo;
 ```
 
 There is a long history of marking "private" members with dangling underscores in JavaScript, beginning with SpiderMonkey adding nonstandard methods such as `__defineGetter__()`. Since that time, using a single underscore prefix has become the most popular convention for indicating a member is not part of the public interface of an object.
@@ -26,8 +26,8 @@ Examples of **incorrect** code for this rule:
 ```js
 /*eslint no-underscore-dangle: "error"*/
 
-var foo_;
-var __proto__ = {};
+let foo_;
+const __proto__ = {};
 foo._bar();
 ```
 
@@ -40,10 +40,10 @@ Examples of **correct** code for this rule:
 ```js
 /*eslint no-underscore-dangle: "error"*/
 
-var _ = require('underscore');
-var obj = _.contains(items, item);
+const _ = require('underscore');
+const obj = _.contains(items, item);
 obj.__proto__ = {};
-var file = __filename;
+const file = __filename;
 function foo(_bar) {};
 const bar = { onClick(_bar) {} };
 const baz = (_bar) => {};
@@ -74,7 +74,7 @@ Examples of additional **correct** code for this rule with the `{ "allow": ["foo
 ```js
 /*eslint no-underscore-dangle: ["error", { "allow": ["foo_", "_bar"] }]*/
 
-var foo_;
+let foo_;
 foo._bar();
 ```
 
@@ -89,7 +89,7 @@ Examples of **correct** code for this rule with the `{ "allowAfterThis": true }`
 ```js
 /*eslint no-underscore-dangle: ["error", { "allowAfterThis": true }]*/
 
-var a = this.foo_;
+const a = this.foo_;
 this._bar();
 ```
 
@@ -106,7 +106,7 @@ Examples of **correct** code for this rule with the `{ "allowAfterSuper": true }
 
 class Foo extends Bar {
   doSomething() {
-    var a = super.foo_;
+    const a = super.foo_;
     super._bar();
   }
 }
@@ -123,7 +123,7 @@ Examples of **correct** code for this rule with the `{ "allowAfterThisConstructo
 ```js
 /*eslint no-underscore-dangle: ["error", { "allowAfterThisConstructor": true }]*/
 
-var a = this.constructor.foo_;
+const a = this.constructor.foo_;
 this.constructor._bar();
 ```
 

Diff for: docs/src/rules/strict.md

@@ -210,7 +210,7 @@ function foo() {
     }
 }());
 
-var foo = (function() {
+const foo2 = (function() {
     "use strict";
 
     return function foo(a = 1) {