JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" name="foto-1">
<input type="text" name="foto-2">

JavaScript

var total = 10;
var inputs = document.querySelectorAll('input');
for (var i = 0; i < inputs.length; i++) {
    inputs[i].addEventListener('keyup', checkInputs);
}

function checkInputs(e) {
    var sum = [].map.call(inputs, function (i) {
        return parseFloat(i.value) || 0;
    }).reduce(function (a, b) {
        return a + b;
    });
    console.log(sum);
    if (sum > total) {
        alert('valor grande demais!');
        this.value = 0;
    }
}