Send XMLHttpRequest When User stops writing

I Just want to send request when user stops writing... i seem to have stopped extra spam by (str.length > 3) this. But What i need is when user stops writing this script gets the input value and send it forward.

This is the updated code right now.

function debounce(func, wait, immediate) {
    var timeout;
    return function() {
        var context = this, args = arguments;
        var later = function() {
            timeout = null;
            if (!immediate) func.apply(context, args);
        };
        var callNow = immediate && !timeout;
        clearTimeout(timeout);
        timeout = setTimeout(later, wait);
        if (callNow) func.apply(context, args);
    };
};


var server = window.location.hostname;
var pathname = window.location.href.split('/');
pathname = (pathname[3]);
var myEfficientFn = debounce(function() {
function showHint(str) {
    if (str.length === 0) { 
        document.getElementById("search-search"suggest-home").innerHTML = "";
    } if (str.length > 3)  {
        var xmlhttp = new XMLHttpRequest();
        xmlhttp.onreadystatechange = function() {
            if (this.readyState == 4 && this.status == 200) {
               // this.responseText;
                var repox = JSON.parse(this.responseText);
                var wrapper = document.getElementById("search-search"suggest-home");
                var myhtml = '<ul>';'<ul style="margin-bottom: 0;min-width: 296px;">';
                for (var i = 0; i < repox.length; i++) {
                var repo = repox[i];
                console.log(repo.url);
                if(repo.type == "breakJios12""ios11"){
                myhtml += '<p>'+ repo.2212+'</p>';"<li>";

                }
                if(repo.type == "breakJios11""ios"){
                myhtml += '<p>'+ repo.2213+'</p>';"<li>";
                }
                }
                myhtml += '<li class="ss-bottom" style="padding: 0; border-bottom: none;"><a href="https://'+  server +'/?s='+encodeURIComponent(str).replace('%20','+')+'" id="suggest-all">View all</a></li>';

                wrapper.innerHTML = myhtml;
            }else {
    // Check back again 1 sec later
    setTimeout(checkState, 1000);
  }
        };
        xmlhttp.open("GET", "https://"+ server +"/test/"+str, true);
        xmlhttp.send();


    }
}
window.onload = showHint(str);
}, 250);
window.addEventListener('resize', myEfficientFn);

Edit Thanks to @Emiel Zuurbier Code works now