read value from input field javascript code example

Example 1: Javascript get text input value

var inputValue = document.getElementById("myTextInputID").value;

Example 2: insert value to html input with javascript variable

function product(a, b) {
   return a * b;
}
function setInputValue(input_id, val) {
    document.getElementById(input_id).setAttribute('value', val);
}

Example 3: js get value from form input

// having form like this

<form>
  <div>
  	<label for="number">Give me number</label>
	<input type="number" id="number">
  </div>
  <div>
    <button class="btn">Click</button>
  </div>
</form>

// this is how u get a value (number)
document.querySelector("form").addEventListener("submit", get_number);
function get_number(e){
    const n = document.getElementById("number").value;
    console.log('n:', n)
    e.preventDefault();
}