batch-process.js

// Based on Nicholas C Zakas' function in High Performance Javascript

function batchProcess(items, process, callback) {
    // Create a copy of the original items array so that our side effects                                                                  
    // (calling .shift()) don't pollute anything outside of this scope.                                                                    
    var todo = items.slice(0);

    setTimeout(function () {
        var start = +new Date, result = true;

        // Process the items in batch for 50ms, or until the iteration is                                                                  
        // canceled (by the process function returning false).                                                                             
        while
            (result !== false
             && todo.length > 0
             && ((+new Date) - start < 50))
        {
              result = process(todo.shift());
        }

        // When the 50ms is up, let the UI thread update by defering the rest of                                                           
        // the iteration in a setTimeout.                                                                                                  
        if (todo.length > 0 && result !== false) {
             setTimeout(arguments.callee, 25);
        } else {
             callback(items);
        }
    }, 25);
};