Get a form input field value with javascript

You can use document.getElementById("input_field_id"); or you can use:

var form=document.forms["form_name"];
var input_value= form["input_field_id"].value;

Note that the typeof(input_value) will be string even if the type of the input field is “number”.

So even if you enter an integer in the field Number.isInteger(input_value) will return false and typeof(input_value) will return string.