script.js

const calculateTemp = () => {
    const numberTemp = document.getElementById('temp').value;
    const tempSelected = document.getElementById('temp_diff');
    const valueTemp = temp_diff.options[tempSelected.selectedIndex].value;


    const celTofeh=(cel)=>{
         let fahrenheit = Math.round((cel*9/5)+32);
         return fahrenheit;
    }

    const fehTocel=(feh)=>{
         let celsius = Math.round((feh -32)* 5/9);
         return celsius;
    }
    let result ;
    if(valueTemp == 'cel'){
         result = celTofeh(numberTemp);
         document.getElementById('resultContainer').innerHTML =`= ${result} °Fahrenheit`;
    }else
    {
         result = fehTocel(numberTemp);
         document.getElementById('resultContainer').innerHTML =`= ${result} °Celcius`;

    }
}