app/static/user/registeration.js

function check_username(elem){
    if(elem.value!=''){
        fetch(`/user/is_username_available/?username=${elem.value}`,{
            method:"GET",
            
        }).then(function(response){
            return response.json();
        }).then(function(response){
            // show a indicator that this username is available
            if(response['available'])
            {
                // show green indicator
                console.log("Username available");
                elem.dataset.valid=true;
                elem.style.borderColor='green';
                elem.style.borderWidth=4;
            }
            else
            {
                // show red indicator
                console.log("Username unavailable");
                elem.dataset.valid=false;
                elem.style.borderColor='red';
                elem.style.borderWidth=4;
            }
        });
    }
}

function check_password_is_matching(confirm_password){
    var password=document.querySelector("#password");
    if(confirm_password.value!=password.value){
        confirm_password.style.borderColor='red';
        confirm_password.style.borderWidth=4;
    }
    else{
        confirm_password.style.borderColor='green';
        confirm_password.style.borderWidth=4;
    }
}

function validate_form(form){
    if(form.username.dataset.valid=="false"){
        document.querySelector("#container>p").style.visibility='visible';
        document.querySelector("#container>p").innerText="username not available";
        return false;
    }
    else if(form.password.value!=form.confirm_password.value){
        document.querySelector("#container>p").style.visibility='visible';
        document.querySelector("#container>p").innerText="password not matching";
        return false;
    }
    else{
        return true;
    }
}

function count_words(elem){
    var count = 0;
          
    // Split the words on each
    // space character 
    var split = elem.value.split(' ');
    
    // Loop through the words and 
    // increase the counter when 
    // each split word is not empty
    for (var i = 0; i < split.length; i++) {
        if (split[i] != "") {
            count += 1;
        }
    }
    console.log("count:",count)
}