Custom Button Example: Mass Delete

Use this sample code:

{!REQUIRESCRIPT("/soap/ajax/9.0/connection.js")} 

var records = {!GETRECORDIDS( $ObjectType.Event )}; 
var taskRecords = {!GETRECORDIDS( $ObjectType.Task)}; 
records = records.concat(taskRecords); 


if (records[0] == null) { 
alert("Please select at least one record.") } 
else { 

var errors = []; 
var result = sforce.connection.deleteIds(records); 
if (result && result.length){ 
var numFailed = 0; 
var numSucceeded = 0; 
for (var i = 0; i < result.length; i++){ 
var res = result[i]; 
if (res && res.success == 'true'){ 
numSucceeded++; 
} else { 
var es = res.getArray("errors"); 
if (es.length > 0) { 
errors.push(es[0].message); 
} 
numFailed++; 
} 
} 
if (numFailed > 0){ 
alert("Failed: " + numFailed + "\nSucceeded: " + numSucceeded + " \n Due to: " + errors.join("\n")); 
} else { 
alert("Number of records deleted: " + numSucceeded); 
} 
} 
window.location.reload(); 
}