added answers

made a least and greater nested functions. Created if else statement to proceed with the loop if output is a number and not a negative number.

05_sumAll/sumAll.js

@@ -1,10 +1,45 @@
+/*function greater(num1, num2){
+   if(num1 > num2){
+    return num1;
+   } else if(num2 > num1){
+   return num2;
+   }
+  }
+  function least(num1, num2){
+   if(num1 < num2){
+    return num1;
+   } else if(num2 < num1){
+   return num2;
+   }
+  }
+*/
+
 const sumAll = function(num1, num2) {
     let sum = 0;
- for( let i = num1; i <= num2; i++){
+      if( Math.sign(num1 || num2) !== -1 && typeof(num1 && num2) === "number" ){
+    const least = (num1,num2) =>{
+      if(num1 < num2){
+      return num1;
+     } else if(num2 < num1){
+      return num2;
+     }
+   }
+    
+    const greater = (num1,num2) =>{
+      if(num1 > num2){
+          return num1;
+        } else if(num2 > num1){
+         return num2;
+        }
+     }
+     
+ for( let i = least(num1,num2); i <= greater(num1,num2); i++){
     sum+=i;
  }
  return sum;
-};
-sumAll(1, 4);
+} else{
+   return "ERROR";
+}};
+console.log(sumAll(1, 4));
 // Do not edit below this line
 module.exports = sumAll;