原生js 封裝get ,post, delete 請求的實例

function api(url,opt,methods) {
 return new Promise(function(resove,reject){
 methods = methods || 'POST';
 var xmlHttp = null;
 if (XMLHttpRequest) {
 xmlHttp = new XMLHttpRequest();
 } else {
 xmlHttp = new ActiveXObject('Microsoft.XMLHTTP');
 };
 var params = [];
 for (var key in opt){
 if(!!opt[key] || opt[key] === 0){
 params.push(key + '=' + opt[key]);
 }
 };
 var postData = params.join('&');
 if (methods.toUpperCase() === 'POST') {
 xmlHttp.open('POST', url, true);
 xmlHttp.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded;charset=utf-8');
 xmlHttp.send(postData);
 }else if (methods.toUpperCase() === 'GET') {
 xmlHttp.open('GET', url + '?' + postData, true);
 xmlHttp.send(null);
 }else if(methods.toUpperCase() === 'DELETE'){
 xmlHttp.open('DELETE', url + '?' + postData, true);
 xmlHttp.send(null);
 }
 xmlHttp.onreadystatechange = function () {
 if (xmlHttp.readyState == 4 && xmlHttp.status == 200) {
 resove(JSON.parse(xmlHttp.responseText));
 }
 };
 });
 }
 export default api;