Get value from an input text in javascript

Colleagues, I have the following scenario:

I have an input

input type="text" id="myField3" name="myField3" ng-model="selected"/>

I need to play the contents of this input in a variable in javascript:

<script>
var escopo = document.getElementById('myField3').value;
console.log(escopo);
</script>

Nothing returns me in the log of the variable. The content of the input is correct.