Conversions now work between already defined values.

unit-conversion/src/features/ending-number-output/endingNumberOutput.js

+/* eslint-disable no-magic-numbers */
 import { useSelector } from 'react-redux';
-import { selectCurrentOutputUnit } from '../unit-selector/unitSelectorSlice';
-import { selectDesiredConversionNumber } from '../number-input-field/numberInputFieldSlice';
+import { selectCurrentOutputUnit, selectCurrentInputUnit} from '../unit-selector/unitSelectorSlice';
+import { selectNumberOfUnits } from '../number-input-field/numberInputFieldSlice';
 
 export function EndingNumberOutput() {
+  const conversionTable = {
+    // To use these conversion multiply your specified unit with
+    // its number to get meters.
+    unitsToMeters: {
+      km: 1000,
+      m: 1.0,
+      cm: 1 / 100,
+      ft: 1 / 3.281,
+      in: 1 / 39.3701,
+    },
+    // Multiply a number of meters by one of these conversions to
+    // get that number of units.
+    metersToUnits: {
+      km: 1 / 1000,
+      m: 1.0,
+      cm: 100,
+      ft: 3.281,
+      in: 39.3701,
+    },
+  };
+
+  const currentInputUnit = useSelector(selectCurrentInputUnit);
   const currentOutputUnit = useSelector(selectCurrentOutputUnit);
-  const unconvertedNumber = useSelector(selectDesiredConversionNumber);
-  const convertedNumber = unconvertedNumber * 100;
+  const numberOfUnits = parseFloat(useSelector(selectNumberOfUnits));
+  const numberOfMeters = numberOfUnits * conversionTable.unitsToMeters[currentInputUnit];
+  let convertedNumber = numberOfMeters * conversionTable.metersToUnits[currentOutputUnit];
+
+  if (isNaN(convertedNumber)) {
+    convertedNumber = 'Please enter number to convert to ';
+  }
+
   return (
     <div>
       <h1>{convertedNumber} {currentOutputUnit}</h1>

unit-conversion/src/features/number-input-field/numberInputField.js

 import { useSelector, useDispatch } from 'react-redux';
 import { selectCurrentInputUnit } from '../unit-selector/unitSelectorSlice';
-import { setDesiredConversionNumber } from './numberInputFieldSlice';
+import { setNumberOfUnits } from './numberInputFieldSlice';
 
 export function NumberInputField() {
   const currentInputUnit = useSelector(selectCurrentInputUnit);
@@ -9,7 +9,7 @@ export function NumberInputField() {
 
   function handleChange(e) {
     const currentNumber = e.target.value;
-    dispatch(setDesiredConversionNumber(currentNumber));
+    dispatch(setNumberOfUnits(currentNumber));
   }
 
   function handleSubmit(e) {

unit-conversion/src/features/number-input-field/numberInputFieldSlice.js

@@ -6,7 +6,7 @@ const numberInputFieldSlice = createSlice({
     numberToConvert: 0,
   },
   reducers: {
-    setDesiredConversionNumber: (state, action) => {
+    setNumberOfUnits: (state, action) => {
       const numToConvert = action.payload;
       return {
         ...state,
@@ -18,9 +18,9 @@ const numberInputFieldSlice = createSlice({
 export default numberInputFieldSlice;
 
 export const {
-  setDesiredConversionNumber,
+  setNumberOfUnits,
 } = numberInputFieldSlice.actions;
 
-export function selectDesiredConversionNumber(state) {
+export function selectNumberOfUnits(state) {
   return state.numberInputField.numberToConvert;
 }