Package Exports

@qiwi/decorator-utils

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Readme

decorator-utils

Motivation

— Decorator, what's that?
— It's just a proposal "aspect" syntax for JS.
— How does it work?
— Addy Osmany's answer
— Is there any ready solution?
— There're many awesome things around. Look at core-decorators and lodash-decorators.
— Do I need this lib?
— You should try this one before: decorator-utils by Luke Horvat
— ...
— Just give a chance to Google
— ...
— How about writing your own? Netanel Basal's practical tips may be very helpful.
— ...
— Yes, go ahead.

NOTE

There's no right way to support both decorator types: with @parentheses() and @plain. Holy War Thread: https://github.com/wycats/javascript-decorators/issues/23

Install

yarn add @qiwi/decorator-utils

Usage

Method

 const decorator = constructDecorator((targetType, target, param) => {
          if (targetType === METHOD) {
            return value => param || 'qux'
          }
        })

        class Foo {
          @decorator()
          foo () { return 'bar' }
          @decorator('BAZ')
          baz () { return 'baz' }
        }

Class

const decorator = constructDecorator((targetType, target) => {
          if (targetType === CLASS) {
            return class Bar extends target {
              constructor (name, age) {
                super(name)
                this.age = age
              }
            }
          }
        })

        @decorator()
        class Foo {
          constructor (name) {
            this.name = name
          }
          foo () { return 'bar' }
        }

Field & Param

    import {createDecorator, FIELD, PARAM} from '@qiwi/decorator-utils'
    
    const meta: any = {}
    const decorator = constructDecorator(({
        propName,
        paramIndex,
        targetType,
        target,
        args: [param]
    }: IDecoratorHandlerContext) => {
      if (targetType === PARAM) {
        if (propName && typeof paramIndex === 'number') {
          meta[propName] = meta[propName] || {}
          meta[propName][paramIndex] = target
        }
      }

      if (targetType === FIELD) {
        if (propName) {
          meta[propName] = param
        }
      }

    })

    class Foo {
      @decorator('arg')
      foo = 'bar'

      bar(one: any, @decorator() two: any) {
        return 'bar'
      }
    }

/**
    Now `meta` is smth like:
    {
      foo: 'arg',
      bar: {
        1: Foo.prototype.bar,
      },
    }
*/

Also you may apply decorator to the class, but decorate its methods:

const decorator = constructDecorator((targetType, target) => {
      if (targetType === METHOD) {
        return () => {
          return target().toUpperCase()
        }
      }
    })

    @decorator()
    class Foo {
      foo () { return 'bar' }
      baz () { return 'baz' }
    }