CRM 2011 with JavaScripts

How to show/hide filed

Xrm.Page.ui.controls.get("city").setVisible(true/false);



How to clear filed

Xrm.Page.getAttribute("city").setValue(null);

How to enable/disable

Xrm.Page.ui.controls.get("city").setDisabled(true/false);

Modify Field Label Tooltip 

document.getElementById("field_name_c").setAttribute("title","tooltip text");

Modify Lookup Button Tooltip 



document.getElementById("field_name").setAttribute("title","tooltip text”);



Set required Filed



function SetRequirementLevelNon(fieldName) {
    var type = Xrm.Page.data.entity.attributes.get(fieldName);
    type.setRequiredLevel("none");
}

function SetRequirementLevel(fieldName) {
    var type = Xrm.Page.data.entity.attributes.get(fieldName);
    type.setRequiredLevel("required");
}