I am making a calculator app with multiple themes and everything works locally but the problem is occuring on the github pages. Each theme for the calculator has its own css file and I am using javascript to change href of the link tag based on the selected theme (theme-1 is selected by default):

HTML:

<link rel="stylesheet" id="themeStyleSheet" href="styles/themes/theme-1.css">

Javascript:

const themeSelector = document.querySelector('#themeSelector');
const themeStyleSheet = document.querySelector('#themeStyleSheet');
let themeValue = 1;

function lastSelectedTheme(){
    themeValue = localStorage.getItem('selectedTheme');
    if(themeValue === '1'){
        themeStyleSheet.href = 'styles/themes/theme-1.css';
        themeSelector.value = localStorage.getItem('toggleValue');
    }
    else if(themeValue === '2'){
        themeStyleSheet.href = 'styles/themes/theme-2.css';
        themeSelector.value = localStorage.getItem('toggleValue');
    }
    else if(themeValue === '3'){
        themeStyleSheet.href = 'styles/themes/theme-3.css';
        themeSelector.value = localStorage.getItem('toggleValue');
    }
}

When I view my page using github it automatically adds '/' in the beginning of the href while there is no '/' in the original javascript code which is causing the problem (if I remove '/' manually from the developer console then it works)

How do I stop / being added to the href?

Github Repo: https://github.com/FaDiiiLeo/calculator