To conceal or reveal a field using a client script in ServiceNow, observe the subsequent steps. Firstly, identify the targeted field that necessitates hiding or showing. Subsequently,devise a client script, specifically an "onLoad" or "onChange" script, contingent upon the intended triggering event. Within the script, employ JavaScript to access the field element and govern its display property. To conceal the field, set the style.displaypropertyto"none". Conversely, to disclose the field, assign the style.display property an appropriate value, such as "block" or "inline". Ultimately, preserve and assess the client script to ascertain the field's visibility behavior.