javascript 实现jsonp

function jsonp(url, callback) {

var callbackName = 'jsonp_callback_' + Math.round(100000 * Math.random());

window[callbackName] = function(data) {

    delete window[callbackName];

    document.body.removeChild(script);

    callback(data);

};



var script = document.createElement('script');

script.src = url + (url.indexOf('?') >= 0 ? '&' : '?') + 'callback=' + callbackName;

document.body.appendChild(script);

}

jsonp('http://www.helloword.com', function(data) {

alert(data);

});