Todo List Application Code in Pure JavaScript
Ok so, your code is overall looking nice, but a few changes could be made:



It's important to make sure you leave whitespace around your operators, like:


addRecordForm.style.display="none";
                           ^^



Could use whitespace around the operators.



I try not to suggest ternaries very often, but I believe that triggerAddRecordForm could be simplified with the use of one.


function triggerAddRecordForm() {
    if(addRecordFormVisibility === false) {
        addRecordForm.style.display="block";
        addRecordFormVisibility = true;
    } else {
        addRecordForm.style.display="none";
        addRecordFormVisibility = false;
    }
}



into:

function triggerAddRecordForm() {
    addRecordForm.style.display = addRecordFormVisiblity ? "none" : "block";
    addRecordFormVisibility = !addRecordFormVisibility;
}


On the subject of triggerAddRecordForm(), in general you shouldn't compare to false, then else it. You should leave the check empty (checks if the variable is true) like so:

if(addRecordFormVisibility) {
    doStuff();
} else {
    doOtherStuff();
}




In submit(), you could improve errors.innerHTML = ''.
Why don't you just set errors to document.getElementById('errors').innerHTML instead, seeing as you don't use errors other than for that?

In submit() you should also improve your line spacing as well, as it seems a little strange.