# Practice on timers and working with the DOM in JavaScript

Let us have an input:

`<input id="elem" value="1">`

Let's make a timer that every second increments the value of the `value` attribute of our input by one:

`let elem = document.querySelector('#elem'); setInterval(function() { elem.value = Number(elem.value) + 1; }, 1000);`

Explain why the `Number` function is used in the above code. What happens if you don't write this function in this code?

Let the input in the `value` attribute initially contain the number `10`. Start a timer that will decrease this number by one every second.

Modify the previous task so that as soon as the content of the input becomes zero, the timer stops running.

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