TypeScript

In Pro, TypeScript is used as the default development language. The benefits of TypeScript are no longer necessary. Both development costs and maintenance costs can be greatly reduced. It is a must for middle and back-end development. Here are several dimensions to talk about the best practices for TypeScript in Pro.

When is type recommended and when is interface used?

It is recommended to use type at all times. Type is more like a variable. Compared with interface, the characteristics of type are as follows:

-The expression function is more powerful, not limited to object/class/function -To extend an existing type, a new type needs to be created, and the name cannot be duplicated -Support more complex type operations

Basically all types expressed with interface have their equivalent type expressions. In the course of practice, we also found that a type can only be expressed by interface, but cannot be expressed by type, that is, attaching attributes to functions.

interface FuncWithAttachment {
  (param: string): boolean;
  someProperty: number;
}

const testFunc: FuncWithAttachment = {};
const result = testFunc('mike'); // Type reminder
testFunc.someProperty = 3; // Type reminder

Define interface data

Any project is inseparable from the processing of data and interfaces. Splicing data and interfaces is one of the main tasks of forming business logic and front-end. Defining the TypeScript type of data returned by the interface can reduce a lot of maintenance costs and the time of querying apis.

In Pro, it is recommended to define the type of interface data in src/services/API.d.ts. Take basic user information as an example:

declare namespace API {
  // Basic user information
  export type CurrentUser = {
    avatar?: string;
    name?: string;
    title?: string;
    group?: string;
    signature?: string;
    tags?: {
      key: string;
      label: string;
    }[];
    userid?: string;
    access?: 'user' | 'guest' | 'admin';
    unreadCount?: number;
  };
}

There are no type definitions in many projects, and websites such as json2ts are recommended for automatic conversion.

We can use it easily when using it. Files ending with d.ts will be imported to the global by TypeScript by default, but the import syntax cannot be used. If you need to quote, you need to use triple slashes.

export async function query() {
  return request<API.CurrentUser[]>('/api/users');
}

// props
export type UserProps = {
  userInfo: API.CurrentUser;
};

Generic

We don't recommend writing generics when developing in industry code, but in order to get a better typescript experience, we may need to understand the generic tips of commonly used component libraries. Here is a brief list.

import ProForm from '@ant-design/pro-form';
import ProTable, { ActionType } from '@ant-design/pro-table';
import React, { useState, useRef } from 'react';

type DataType = {};

const Page = () => {
  // The generic type of useState will become the type of state
  const [state, setState] = useState<string>('');
  // The type of useRef will be set to the type of actionRef.current
  const actionRef = useRef<ActionType>();

  // click uses React.MouseEvent plus dom type generic
  // HTMLInputElement represents the input tag Another commonly used one is HTMLDivElement
  const onClick = (e: React.MouseEvent<HTMLInputElement>) => {};
  // onChange uses React.ChangeEvent plus dom type generic
  // Generally HTMLInputElement, HTMLSelectElement may also be used
  const onChange = (e: React.ChangeEvent<HTMLInputElement>) => {};
  return (
    <>
      {'ProForm sets generics to agree on the parameter types of interfaces such as onFinish'}
      <ProForm<DataType> />
      {`
        DataType sets the type of row in render,
        Params is the submission type of the parameter
        ValueType represents a custom valueType type, ProTable will automatically merge
      `}
      <ProTable<DataType, Params, ValueType> />
      <input onClick={onClick} onChange={onChange} />
    </>
  );
};

Define n ways to write a component

const WrapComponent: React.FC<ExtendedProps> = (props) => {
  // return ...
};

export default WrapComponent;

// or
export default function (props: React.PropsWithChildren<SpinProps>) {
  // return ...
}

umi common types

Umi has helped us to encapsulate in many places. If we know the specific type, we can reduce a lot of any.

Page related

IRouteComponentProps is the props type of the component configured in config.ts, which brings some react-router related props

export interface IRouteComponentProps<
  Params extends { [K in keyof Params]?: string } = {},
  Query extends { [K in keyof Query]?: string } = {}
> {
  children: JSX.Element;
  location: Location & { query: Query };
  route: IRoute;
  routes: IRoute[];
  history: History;
  match: match<Params>;
}

We can use it like this in the page:

import React from 'antd';
import { IRouteComponentProps } from 'umi';

const Page: React.FC<IRouteComponentProps> = () => {
  return <Layout />;
};

Add parameters for Window

Front-end development is largely about dealing with Window. Sometimes we have to add parameters to Window, such as various statistical codes. Provide a way to add parameters in TypeScript. Define as follows in /src/typings.d.ts:

interface Window {
  ga: (
    command: 'send',
    hitType: 'event' | 'pageview',
    fieldsObject: GAFieldsObject | string,
  ) => void;
  reloadAuthorized: () => void;
}

If you don't want to add it in Window, but want to use it globally, such as parameters injected via define, we inject it in /src/typings.d.ts via the declare keyword.

declare const REACT_APP_ENV: 'test' | 'dev' | 'pre' | false;

These examples can all be seen in /src/typings.d.ts.

Type of component

Antd is a very convenient set of UI libraries. In order to use it better, we need to understand some of its types.

Form

There are many commonly used types in Form, and most of them can be derived from 'antd/es/form. Here are some of the most commonly used ones.

The form type generated by using Form.useForm() in antd@4 is FormInstance. FormItemProps is also a commonly used type. We can use this type to encapsulate FormItem and add our own logic.

import { FormInstance, FormItemProps } from 'antd/es/form';

const [form] = Form.useForm();

// save ref
const ref = useRef<FormInstance>();
ref.current = form;

Due to the variability of form, the values ​​returned by form.getFieldsValue(); are all of the Store type, so we can directly as as we want parameters for ourselves.

const user = form.getFieldsValue() as API.CurrentUser;

Table

ProTable is recommended here, the types are relatively clear, examples of commonly used types.

import { ProColumns, ActionType } from '@ant-design/pro-table';

const columns: ProColumns<API.CurrentUser>[] = [
  {
    title: 'Name',
    dataIndex: 'name',
    hideInSearch: true,
  },
];

const actionRef = useRef<ActionType>();

export default <ProTable actionRef={actionRef} />;

In addition, TablePaginationConfig and TableRowSelection are more commonly used. Special attention should be paid when using both of these generic types.

import { TablePaginationConfig } from 'antd/es/table/Table';
import { TableRowSelection } from 'antd/es/table/interface';

const pagination: TablePaginationConfig = {
  pageSize: 20,
  total: 2000,
  onChange: (current) => {},
};

const rowSelection: TableRowSelection = {
  selectedRowKeys: [],
  onChange: (keys, rows) => {},
};

Some small pits

React.ReactText[]

string[]|number[] is not the same as (string|number)[], in this case, just use React.ReactText[] directly.

React.forwardRef

If we use the function component, it may report an error that ref cannot be found. At this time, we need to use React.forwardRef, but it should be noted that the type must also be modified accordingly.

-React.FC<CategorySelectProps>
+ React.ForwardRefRenderFunction<HTMLElement, CategorySelectProps>

Dynamic increase

Sometimes I need to dynamically update the key of an Object. For convenience, we can set the key to any, so that any key can be used, and JSON.parse is unnecessary.

type Person = {
  name: string;
  age?: number;
  [propName: string]: any;
};

Value can be null or undefined

It's very simple in 3.8, just obj?.xxx.

There is no typescript definition in a library

We can directly define it as any.

declare module 'xxx';

import xxx from 'xxx';

@ts-ignore

Sometimes the type error is component, but it looks very uncomfortable. It will always compile and report errors, so you can use @ts-ignore to ignore it temporarily.

// @ts-ignore
xxxx;

After all, TypeScript is a markup language. When you need to use any, you don't need to be hesitant to use any. When encountering dynamic code, you might as well use as unknown as XXX, which can save a lot of time.