In Javascript, does someone/anyone have a exhaustive list of key combination to avoid. For example a textbox sending webservice requests for each keypress. It often happens for key combinations like HOME[for cursor returning to start of textbox] , DELETE, SHIFT + HOME + DELETE the event fires and same request params is sent to webservice.[I know caching query results will solve for this scenario but what about other]. I would love to see a list for this, i couldn't find a similar question before hence this Update: Since the earlier question title seemed too way off and likely closable i changed it. I would like to know how to optimize this process of sending request in ajax manner less intensive.

Assuming the user is writing in a textarea or input, you can check the value of that element for each keystroke; if it's different from its last value, send it to the server. If it's the same, then do nothing.

Example:

function updateOnKeypress(input) {
    var lastValue;
    input.addEventListener('keypress', function() {
        if( input.value.trim() !== lastValue ) {
            // trim() isn't available in every browser, but you can add it
            // Of course, if leading/trailing whitespace is supposed to trigger
            // a request, then skip the trim()
            lastValue = input.value.trim();
            // … send value to server
        }
    });
}

You might also want to throttle the number of requests with a timer, so not every change results in a request to the server. For instance, for each change start a timeout (say, 0.3 seconds), and then send the value when the timer executes.

function updateOnKeypressDelayed(input) {
    var lastValue, timer;
    input.addEventListener('keypress', function() {
        if( !timer ) {
            timer = setTimeout(function () {
                if( input.value.trim() !== lastValue ) {
                    lastValue = input.value.trim();
                    timer = null;
                    // … send value to server
                }
            }, 300);
        }
    });
}