How to calculate and display the sum of dates instantly?

Question

Expensive,

I have a situation where I need to create a lease. In the fields, the person who is entering with the data has the options:

*months / *start date / *end date

I would like to know how to do this in Javascript, with instant update. I tested with that solution, but to no avail, for I believe that these are only whole numbers.

I like the method onblur, because the result is generated automatically, based on the user’s choice.

I need a light!

Answer 1

I recommend using the .change on top of the drop with the amount of months.

If you have the string with the initial date, you can create a Date() with this string...and from there add up the amount of months.

And of course, you will also need a date formation, which I advise this:

function formatarData(data) {
    var d = new Date(data),
        mes = '' + (d.getMonth() + 1),
        dia = '' + d.getDate(),
        ano = d.getFullYear();

    if (mes.length < 2) mes = '0' + mes;
    if (dia.length < 2) dia = '0' + dia;

    return [dia, mes, ano].join('/');
}

That is, with your entrance:

var qtdMeses = 6;
var dtInicio = new Date($("#dataInicio").val());
dtInicio.setMonth(dtInicio.getMonth() + qtdMeses); //adicionando meses

$("#dataTermino").val(formatarData(dtInicio));

EDIT:

to dtInicio also has to be formatted before being used... I updated the attribution of it as follows:

var dtInicio = new Date(formatarData($("#dataInicio").val()));

Online example

ANOTHER EDIT:

As I mentioned in the comments, I find the best solution to add N days (since, on January 30 if I add + 1 month, will return NaN, for there is no February 30th... So I have prepared another Online Example and made a change in the structure of events. I created a function to make the date calculation.... this function is called every time the event change() Quantity of months dropdown for "triggado" and every time the start date field loses focus (blur).

$("#meses").change(function() {
    calcularDataTermino();
});

$("#dataInicio").blur(function() {
    calcularDataTermino();
});

function calcularDataTermino() {
  var qtdMeses = parseInt($("#meses").val());
  var qtdDias = 30 * parseInt($("#meses").val()); // sempre 30 dias + de acordo com a quantidade de meses: 1 mês = +30 dias; 2 meses = + 60 dias; 3 meses = 90 dias;
  var dtInicio = new Date(formatarData($("#dataInicio").val()));


  //dtInicio.setMonth(dtInicio.getMonth() + qtdMeses); //+ N qtdMeses
  dtInicio.setDate(dtInicio.getDate() + qtdDias); //+ N dias

  $("#dataTermino").val(formatarData(dtInicio));
}