ajax

function ajax(url, type='json', method='get', data=''){
	return new Promise((resolve, reject)=>{
		// 1.创建xhr
		let xhr = window.XMLHttpRequest ? new XMLHttpRequest() : new ActiveXObject('Microsoft.XMLHttp');
		// 2.创建请求
		xhr.open(method, url, true);
		// 3.设置回调
		xhr.onreadystatechange = ()=>{
			if(xhr.readyState == 4)
				if(xhr.status == 200)
					if(type.toLowerCase() == 'json')
						resolve(JSON.parse(xhr.responseText));
					else
						resolve(xhr.responseText);
				else
					reject('ajax出错=>'+xhr.status);
		}
		// 4.设置请求头
		if(method.toLowerCase() == 'post')
			xhr.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
		// 5.发送请求
		xhr.send(data);
	});
}