@form-create/core/src/frame/fetch.js

FormCreate低代码表单渲染引擎，可以通过 JSON 生成具有动态渲染、数据收集、验证和提交功能的低代码表单。支持6个UI框架，适配移动端，并且支持生成任何 Vue 组件。

// https://github.com/ElemeFE/element/blob/dev/packages/upload/src/ajax.js

import is from '@form-create/utils/lib/type';
import {parseFn} from '@form-create/utils/lib/json';

function getError(action, option, xhr) {
    const msg = `fail to ${action} ${xhr.status}'`;
    const err = new Error(msg);
    err.status = xhr.status;
    err.url = action;
    return err;
}

function getBody(xhr) {
    const text = xhr.responseText || xhr.response;
    if (!text) {
        return text;
    }

    try {
        return JSON.parse(text);
    } catch (e) {
        return text;
    }
}

export default function fetch(option) {
    if (typeof XMLHttpRequest === 'undefined') {
        return;
    }

    const xhr = new XMLHttpRequest();
    const action = option.action;

    xhr.onerror = function error(e) {
        option.onError(e);
    };

    xhr.onload = function onload() {
        if (xhr.status < 200 || xhr.status >= 300) {
            return option.onError(getError(action, option, xhr), getBody(xhr));
        }

        option.onSuccess(getBody(xhr));
    };

    xhr.open(option.method || 'get', action, true);

    let formData;
    if (option.data) {
        if ((option.dataType || '').toLowerCase() !== 'json') {
            formData = new FormData();
            Object.keys(option.data).map(key => {
                formData.append(key, option.data[key]);
            });
        } else {
            formData = JSON.stringify(option.data);
            xhr.setRequestHeader('content-type', 'application/json');
        }
    }


    if (option.withCredentials && 'withCredentials' in xhr) {
        xhr.withCredentials = true;
    }

    const headers = option.headers || {};

    Object.keys(headers).forEach(item => {
        if (headers[item] !== null) {
            xhr.setRequestHeader(item, headers[item]);
        }
    });
    xhr.send(formData);
}

export function asyncFetch(config) {
    return new Promise((resolve, reject) => {
        fetch({
            ...config,
            onSuccess(res) {
                let fn = (v) => v;
                const parse = parseFn(config.parse);
                if (is.Function(parse)) {
                    fn = parse;
                } else if (parse && is.String(parse)) {
                    fn = (v) => {
                        parse.split('.').forEach(k => {
                            if (v) {
                                v = v[k];
                            }
                        })
                        return v;
                    }
                }
                resolve(fn(res));
            },
            onError(err) {
                reject(err);
            }
        })
    });
}