自定义AJAX函数中正在执行两个回调函数

Question

I have created a custom GET and POST function in javascript to handle my AJAX requests. When I try to make a call, fail callback is executed first and then the done callback. The response from AJAX is a valid JSON string and I do not understand why this is happening. Only done callback must be executed if the response is valid JSON.

get('ajax/autocomplete.php', {q: q}, function(data) {
    //done, executed second
}, aww());//Error, executed first

function get() {
    var data,
        done,
        fail,
        done_index = null,
        str = '',
        ajax = new XMLHttpRequest(),
        url = arguments[0];

    for(var i=0; i<arguments.length; i++) {
        if(typeof arguments[i] == 'object') {
            data = arguments[i];

            for(var key in data) {
                if(str != "") str += "&";

                str += key + "=" + encodeURIComponent(data[key]);
            }

            if(str != '') url += '?';
        } else if(typeof arguments[i] == 'function') {
            if(!done_index) {
                done = arguments[i];
                done_index = i;
            }

            if(i != done_index) {
                fail = arguments[i];
            }
        }
    }

    ajax.onreadystatechange = function() {
        console.log(ajax.readyState, ajax.status);

        if(ajax.readyState === XMLHttpRequest.DONE && ajax.status === 200) {
            var response = ajax.responseText;//treat empty response as valid JSON
            if(response.length == 0) response = '""';

            try {
                var json = JSON.parse(response);
                return (done) ? done(json) : false;
            } catch(e) {
                console.log(e);
                return (fail) ? fail() : false;
            }
        }
    };

    ajax.open('get', url + str);
    ajax.send();
}

Answer 1

You're calling the aww() function in the argument list to get() , because you have parentheses after it. You should just pass a reference to the function. It should be:

get('ajax/autocomplete.php', {q: q}, function(data) {
}, aww);