How to write JSONP Ajax request on pure js? [duplicate]

问题

This question already has an answer here:

Making and handling JSONP request using JavaScript (1 answer)

Closed 5 years ago.

$.ajax( { url : '', data: {}, dataType:'jsonp',  jsonpCallback: 'callbackName', type: 'post'
        ,success:function (data) {
        console.log('ok');
        },
        error:function () {
        console.log('error');
        }
        });

How do I write the same functionality in pure JS?

回答1:

In this particular case, you aren't making an ajax call at all, instead you're making a JSONP request. Luckily, these are incredibly easy to replicate and work in all browsers.

var s = document.createElement("script"),
    callback = "jsonpCallback_" + new Date().getTime(),
    url = "http://forexplay.net/ajax/quotes.php?callback=" + callback;
window[callback] = function (data) {
    // it worked!
    console.log(data);
};
s.src = url;
document.body.appendChild(s);

回答2:

var xmlhttp=new XMLHttpRequest();
xmlhttp.open("POST", 'http://forexplay.net/ajax/quotes.php');
xmlhttp.onreadystatechange = function() {
    if (xmlhttp.readyState == XMLHttpRequest.DONE) {
        if(xmlhttp.status == 200){
            console.log('Response: ' + xmlhttp.responseText );
        }else{
            console.log('Error: ' + xmlhttp.statusText )
        }
    }
}
xmlhttp.send(data);

I'm always forgetting about capital and small letters in XMLHttpRequest

来源：https://stackoverflow.com/questions/23702229/how-to-write-jsonp-ajax-request-on-pure-js