# 辅助方法

用于减轻组件渲染的垃圾回收压力。

# pluckFirst

pluckFirst<TArr>(inputs$: Observable<TArr>): Observable<TArr[0]>

提取数组的第一个元素。

类型参数:

  • TArr ArrayLike

参数:

参数名 类型 描述
inputs$ Observable<TArr> An Observable of arraylike.

返回值:

Observable<TArr[0]> Observable of the first item.

Examples:

// An Observable of string
const text$ = useObservable(pluckFirst, [props.text])

# pluckCurrentTargetValue

pluckCurrentTargetValue<TEvent>(
  event$: Observable<TEvent>
): Observable<TEvent["currentTarget"]["value"]>

提取 .currentTarget.value

类型参数:

  • TEvent Event with currentTarget.value.

参数:

参数名 类型 描述
event$ Observable<TEvent> An Observable of events.

返回值:

Observable<TEvent["currentTarget"]["value"]> An Observable of event currentTarget.value.

Examples:

const [onChange, textChange$] = useObservableCallback<
 string,
 React.FormEvent<HTMLInputElement>
>(pluckCurrentTargetValue)

# pluckCurrentTargetChecked

pluckCurrentTargetChecked<TEvent>(
  event$: Observable<TEvent>
): Observable<TEvent["currentTarget"]["checked"]>

提取 .currentTarget.checked

类型参数:

  • TEvent Event with currentTarget.checked.

参数:

参数名 类型 描述
event$ Observable<TEvent> An Observable of events.

返回值:

Observable<TEvent["currentTarget"]["checked"]> An Observable of event currentTarget.checked.

Examples:

const [onChange, checked$] = useObservableCallback<
 boolean,
 React.FormEvent<HTMLInputElement>
>(pluckCurrentTargetChecked)

# identity

identity<T>(value: T): T

返回第一个参数。

类型参数:

  • T Any value.

参数:

参数名 类型 描述
value T Any value.

返回值:

T The first argument.

# useRefFn

带初始化方法的 Ref。

useRefFn<T>(init: function): MutableRefObject<T>

类型参数:

  • T any.

参数:

参数名 类型 描述
init (): T A function that returns a value. Will be called only once.

返回值:

MutableRefObject<T> A Ref object with the returned value.

# useForceUpdate

Force re-renders Component.

useForceUpdate(): () => void

返回值:

() => void A callback which re-renders component when called.