Question: I have a table and each of its `td` has a **unique id** that corresponds to some time intervals (`0800` til `0830`... `0830` til `0900` and so on). 

I have an input text where the user will type the time intervals they want to block. 

If they type an interval that doesn't exist in my table, in other words, if they type an interval that doesn't correspond to any of my `td's id's`, I want to show an alert saying something like `this interval is not available for blocking`.

But, I'm having difficulty to find this id.

I'm doing this:

```
    var horaInicial = $("#horaInicial").val().split(':')[0] + $("#horaInicial").val().split(':')[1]; // this is remover the ":" from a formatted hour

    var verificaHorario = $("#tbIntervalos").find("td").attr("id", horaInicial);

```

But this `verificaHorario` is actually setting all my td's to this horaInicial id.

How can I find the id in my table and if it doesn't exist show some alert?

Answer: 
If you're trying to find an element by id, you don't need to search the table only - it should be unique on the page, and so you should be able to use:

```
var verificaHorario = $('#' + horaInicial);

```

If you need to search only in the table for whatever reason, you can use:

```
var verificaHorario = $("#tbIntervalos").find("td#" + horaInicial)

```
This is one more option to find the element for above question

`$("#tbIntervalos").find('td[id="'+horaInicial+'"]')`