Why is my code giving **"Uncaught SyntaxError: Missing initializer in const declaration"**

Here is the code in question:<br><br>```javascript<br>const mainInputChange = (e) => {<br> appCounter = e.target.value<br> }<br> const secondaryInputChange = (e) => {<br> secondaryCounter = e.target.value<br> }<br> const checkboxClick = () => {<br> .big = !.big<br> }<br>```