extended backbone.js sync function. uses setTimeout to batch multiple saves on one model in one http request.

backbone.js-sync-setTimeout

    // decreases request count on rapid-fire one model saves
    // extended backbone.js sync function. uses setTimeout to batch multiple saves on one model in one http request. 
    // if client side needs immediate answer from server for changes in model attributes, 
    // pass { immediate: true } in model save options if { wait: true } is not used already.
    Backbone._sync=Backbone.sync
    Backbone.sync = function(method, model, options){
        var maxResetCount=5        // how many times to delay save
        var saveBufferSize=3000    // for how many microseconds save is delayed

        var immediate=options['wait'] || options['immediate'] || false

        // init state variables
        if (!_.has(this, 'saveQueue')){
            this.saveQueue={}
        }
        if (!_.has(model, 'saveResetCount')){
            model.saveResetCount=0
        }

        var args=arguments,
            self=this
        // work only on update requests, 
        // because it works safely only on idempotent requests and delete usually is invoked only one time ;)
        if (method==='update' && immediate!==true){
            // if model is in save queue, remove old timeout - it will be replaced by new one
            if (_.has(this.saveQueue, model.id)){
                model.saveResetCount+=1
                if (model.saveResetCount<maxResetCount){
                    console.debug('Backbone.sync: clearing timeout. reset count='+model.saveResetCount)
                    clearTimeout(model.saveTimeoutId)
                }else{
                    console.debug('Backbone.sync: NOT clearing timeout. reset count='+model.saveResetCount)
                }
            }else { // if model is not in save queue, place it in it
                console.debug('Backbone.sync: placing model in save queue')
                this.saveQueue[model.id]=model
            }

            if (model.saveResetCount<maxResetCount){
                model.saveTimeoutId=setTimeout(
                    function(){
                        console.debug('Backbone.sync: delayed sync')
                        delete self.saveQueue[model.id]
                        model.saveResetCount=0
                        Backbone._sync.apply(self, args)
                    },
                    saveBufferSize
                )
            }
        }else{
            return Backbone._sync.apply(self, args)
        }
    }

Instead of using setTimeout you could use the underscore.js "debounce" function fyi...

i wanted to control how many times saving is delayed to prevent loosing big sets of client-side changes.