fix(curriculum): Updated javascript curriculum step 17 descripiton (#53460)

curriculum/challenges/english/15-javascript-algorithms-and-data-structures-22/learn-form-validation-by-building-a-calorie-counter/63b614e6a1f7fe2cef6312dc.md

@@ -7,6 +7,13 @@ dashedName: step-17
 
 # --description--
 
+In programming, it is standard practice to prefix a variable with `is` or `has` to indicate that the variable is a boolean. 
+
+```js
+let isRunning = true;
+let hasCompleted = false;
+```
+
 Declare an `isError` variable and set it to `false`, but use `let` so you can reassign it later.
 
 # --hints--