[docs] Fix typo

CHANGELOG.old.md

@@ -13577,7 +13577,7 @@ _May 24, 2015_
       that you are trying to override, [submit an issue](https://github.com/mui/material-ui/issues/new)
       requesting to have it added.
     - _If you are using any of Material UI's Less files:_ These files have been
-      refactored into their [own javascript files](https://github.com/mui/material-ui/tree/css-in-js/src/styles)
+      refactored into their [own JavaScript files](https://github.com/mui/material-ui/tree/css-in-js/src/styles)
       and can be accessed like so `var FILENAME = require('material-ui').Styles.FILENAME;`.
       Material UI has moved away from being a CSS Framework to being simply a
       set of React components.

docs/data/material/experimental-api/classname-generator/classname-generator.md

@@ -20,7 +20,7 @@ By default, Material UI generates a global class name for each component slot. F
 </button>
 ```
 
-To customize all the class names generated by Material UI components, create a separate javascript file to use the `ClassNameGenerator` API.
+To customize all the class names generated by Material UI components, create a separate JavaScript file to use the `ClassNameGenerator` API.
 
 ```js
 // create a new file called `MuiClassNameSetup.js` at the root or src folder.
@@ -132,7 +132,7 @@ ClassNameGenerator.configure(
 );
 ```
 
-Then import the file in the main javascript source based on the framework.
+Then import the file in the main JavaScript source based on the framework.
 
 ### Next.js
 

docs/data/material/experimental-api/css-theme-variables/overview.md

@@ -80,7 +80,7 @@ createTheme({
     MuiButton: {
       styleOverrides: {
         root: ({ theme }) => ({
-          // use javascript conditional expression
+          // use JavaScript conditional expression
           color: theme.palette.mode === 'dark' ? '#fff' : theme.palette.primary.main,
         }),
       },