subtraction: fixed steps and carry; let user input last carry; autofocus res input; log result

src/Subtraction.js

@@ -45,19 +45,19 @@ function Subtraction() {
     }else{
       // add input number to result array
       resArr.unshift(imdtRes);
-      if(nosLeft === 0){
-        setShowAlert(true);
-      }
     }
   }
 
-  const handleCarryChange = (e, noOfDigits, idx) => {
-    if(typeof carryArr === "undefined"){
-       setCarryArr(Array(noOfDigits).fill("-"));
-    }
-    let carryArrCopy = [...carryArr]
-    carryArrCopy[idx] = e.target.value
+  const handleCarryChange = (e, noOfDigits, nosLeft) => {
+    let carryArrCopy = [...carryArr];
+    carryArrCopy.unshift(e.target.value);
     setCarryArr(carryArrCopy);
+    let noCarry = carryArrCopy[0] === "0" || carryArrCopy[0] === undefined;
+    if(nosLeft === 0 || (nosLeft === 1 && noCarry) ||
+       // stop after first iteration, numbers left is undefined at first
+       (nosLeft !== nosLeft && realResult.toString().length === 1 && noCarry)){
+      setShowAlert(true);
+    }
   }
 
   const handleSubmit = (e) => {
@@ -76,6 +76,7 @@ function Subtraction() {
       let afterComma = Math.max(...numbers.map(x => afterCommaLen(x)));
       realRes = parseFloat(realRes.toFixed(afterComma));
       setRealResult(realRes);
+      console.log("real result: ", realRes)
 
       let [numbersArr, commaIdx] = numbersToArrOfArr(numbers);
       setNumbers(numbersArr);
@@ -91,7 +92,6 @@ function Subtraction() {
     let labelText = "";
     let nosLeft = imdtResIdx + 1;
     let carryText = "Übertrag = ";
-    let carryOffset = 0;
     let firstDigit = 0;
     let digit = 0;
 
@@ -103,7 +103,7 @@ function Subtraction() {
       if(imdtResIdx === commaIdx){
         handleResChange(".", nosLeft)
         imdtResIdx = imdtResIdx - 1;
-        carryOffset = 1;
+        nosLeft = nosLeft - 1;
       }
 
       if(numbers.length>2){
@@ -127,8 +127,8 @@ function Subtraction() {
           labelText += digit;
 
           if (parseInt(n) === numbers.length - 1){
-            if(carryArr[imdtResIdx+carryOffset]!=="undefind" && carryArr[imdtResIdx+carryOffset] > 0){
-              labelText += " + " + carryArr[imdtResIdx+carryOffset].toString();
+            if(carryArr[0] !== undefined && carryArr[0] > 0){
+              labelText += " + " + carryArr[0].toString();
             }
             if(numbers.length>2){
               labelText += ")";
@@ -142,7 +142,7 @@ function Subtraction() {
       labelText += " + wie viel = " + firstDigit
       labelText = labelText.replace(/ /g, "0")
 
-      if(carryArr[imdtResIdx+carryOffset] > -1 || imdtResIdx === noOfDigits-1){
+      if(carryArr[0] > -1 || imdtResIdx === noOfDigits-1){
         imdtRes = -1;
         imdtResIdx = imdtResIdx - 1;
         nosLeft = nosLeft - 1;
@@ -157,13 +157,13 @@ function Subtraction() {
             onChange={(e) => handleResChange(e, nosLeft)}
             type="text" id="input_result" size="2"
             aria-labelledby="input_result_label" aria-required="true"
-            ref={resInputField}/>
+            ref={resInputField} autoFocus/>
           <br/>
           <label htmlFor="input_carry" id="input_carry_label">
             {carryText}
           </label>
           <input
-            onChange={(e) => handleCarryChange(e, noOfDigits, imdtResIdx)}
+            onChange={(e) => handleCarryChange(e, noOfDigits, nosLeft)}
             type="text" id="input_carry" size="2"
             aria-labelledby="input_carry_label" aria-required="true"
             ref={carryInputField}/>
@@ -192,7 +192,7 @@ function Subtraction() {
 
     let foundComma = false;
     let stepsGridCopy = [];
-    for (let i=0; i<resArr.length-1; i++) {
+    for (let i=0; i<resArr.length; i++) {
       let text = "";
       let trueNumbers = false;
       let idxNumbers = resArr.length - i - 1;
@@ -225,7 +225,7 @@ function Subtraction() {
       }
 
       // ignore indexes without real digits
-      if (resArr[idxNumbers]!=="&nbsp;" || carries[idxCarry]!=="&nbsp;"){
+      if (resArr[idxNumbers]!=="&nbsp;" || (carries[idxCarry]!=="&nbsp;" & carries[idxCarry]!=="0")){
         trueNumbers = true;
       }
 
@@ -290,6 +290,9 @@ function Subtraction() {
       }
     }
     let resCalc = res.join("");
+    if(resCalc.startsWith(".")){
+      resCalc = "0" + resCalc;
+    }
     setResultsGrid([{number: resCalc}]);
     resCalc = parseFloat(resCalc);