show text in span ko js code example

Example 1: how to get value inside span using javascript

var span_Text = document.getElementById("span_Id").innerText;

console.log(span_Text)

Example 2: how to get value inside span using javascript

<script type="text/javascript">
document.getElementById('button1').onChange = function () {
    document.getElementById('hidden_field_id').value = document.getElementById('span_id').innerHTML;
}
</script>