fetch.js

import {baseUrl} from './env'

export default async (type = 'GET', url = '', data = {}) => {
	type = type.toUpperCase();
	url = baseUrl + url;

	if (type == 'GET') {
		let dataStr = ''; //数据拼接字符串
		Object.keys(data).forEach(key => {
			dataStr += key + '=' + data[key] + '&';
		})

		if (dataStr !== '') {
			dataStr = dataStr.substr(0, dataStr.lastIndexOf('&'));
			url = url + '?' + dataStr;
		}
	}

	if (window.fetch) {
		let requestConfig = {
			credentials: 'include',
		  	method: type,
		  	headers: {
		      	'Accept': 'application/json',
	  			'Content-Type': 'application/json'
		  	},
		  	mode: "cors",
		  	cache: "only-if-cached"
		}

		if (type == 'POST') {
			Object.defineProperty(requestConfig, 'body', {
				value: JSON.stringify(data)
			})
		}

		try {
			var response = await fetch(url, requestConfig);
			var responseJson = await response.json();
		}catch (error){
			throw new Error(error)
		}
		
		return responseJson
	}else{
		let requestObj;
		if (window.XMLHttpRequest) {
			requestObj = new XMLHttpRequest();
		} else {
			requestObj = new ActiveXObject;
		}

		let sendData = '';
		if (type == 'POST') {
			sendData = JSON.stringify(data);
		}

		requestObj.open(type, url, true);
		requestObj.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
		requestObj.send(sendData);

		requestObj.onreadystatechange = () => {
			if (requestObj.readyState == 4) {
				if (requestObj.status == 200) {
					let obj = requestObj.response
					if (typeof obj !== 'object') {
						obj = JSON.parse(obj);
					}
					return obj
				}else {
					throw new Error(requestObj)
				}
			}
		}
	}
}