script.js

console.log("hello there")

let theme = localStorage.getItem('theme')

if(theme == null){
    setTheme('blue')
}
else{
    setTheme(theme)
}

let themeDots = document.getElementsByClassName('theme-dots')

for(var i=0; i<themeDots.length;i++){
    themeDots[i].addEventListener('click',function(){
        let mode = this.dataset.mode
        console.log(mode)
        setTheme(mode)
    })
}

function setTheme(mode){
    if(mode == 'light'){
        document.getElementById('theme-style').href = './styles/style.css'
    }
    if(mode == 'blue'){
        document.getElementById('theme-style').href = './styles/blue.css'
    }
    if(mode == 'green'){
        document.getElementById('theme-style').href = './styles/green.css'
    }
    if(mode == 'purple'){
        document.getElementById('theme-style').href = './styles/purple.css'
    }
}

localStorage.setItem('theme',mode)