How to script custom Doctype

yes, i found the files

Sangram i have entered below function to .js file, after doing this changes my forms goes blank

frappe.ui.form.on(‘Measurement Sheet’, {
validate: function(frm) {
frm.trigger(“calculate_area”)
},

length: function(frm) {
	frm.trigger("calculate_area")
},

width: function(frm) {
	frm.trigger("calculate_area")
},

calculate_area: function(frm) {
	if (frm.doc.hsd5 && frm.doc.wsd5){ 
		area = flt(frm.doc.hsd5* frm.doc.wsd5);
		frm.set_value('area', area)
	}
}
refresh: function(frm) {

}

});

Hi, how did you achieve this dark look?

@Yvonne_Nduta…Visit this
https://discuss.frappe.io/t/custom-app-themes-for-erpnext/18598

Thank you so much.