[Slider] Update TypeScript demo to cast types to values (mui#16957)

Author: allypally

docs/src/pages/components/slider/ContinuousSlider.tsx

@@ -14,10 +14,10 @@ const useStyles = makeStyles({
 
 export default function ContinuousSlider() {
   const classes = useStyles();
-  const [value, setValue] = React.useState<number | number[]>(30);
+  const [value, setValue] = React.useState<number>(30);
 
   const handleChange = (event: any, newValue: number | number[]) => {
-    setValue(newValue);
+    setValue(newValue as number);
   };
 
   return (

docs/src/pages/components/slider/RangeSlider.tsx

@@ -15,10 +15,10 @@ function valuetext(value: number) {
 
 export default function RangeSlider() {
   const classes = useStyles();
-  const [value, setValue] = React.useState<number | number[]>([20, 37]);
+  const [value, setValue] = React.useState<number[]>([20, 37]);
 
   const handleChange = (event: any, newValue: number | number[]) => {
-    setValue(newValue);
+    setValue(newValue as number[]);
   };
 
   return (