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<p>침착맨의 미라클 방송을 본받아 미라클 블로그 글쓰기를 해볼까 한다.</p>



<figure><img data-attachment-id="1578" data-permalink="https://01010011.blog/2023/12/31/i-am-%ec%95%bd%ec%86%8d%ec%a2%8b%ec%95%84-promise-vs-promiselike-%ec%9d%98-%ec%b0%a8%ec%9d%b4%ec%a0%90/image-2/" data-orig-file="https://01010011blog.files.wordpress.com/2023/12/image.png" data-orig-size="686,386" data-comments-opened="1" data-image-meta="{&quot;aperture&quot;:&quot;0&quot;,&quot;credit&quot;:&quot;&quot;,&quot;camera&quot;:&quot;&quot;,&quot;caption&quot;:&quot;&quot;,&quot;created_timestamp&quot;:&quot;0&quot;,&quot;copyright&quot;:&quot;&quot;,&quot;focal_length&quot;:&quot;0&quot;,&quot;iso&quot;:&quot;0&quot;,&quot;shutter_speed&quot;:&quot;0&quot;,&quot;title&quot;:&quot;&quot;,&quot;orientation&quot;:&quot;0&quot;}" data-image-title="image" data-image-description="" data-image-caption="" data-medium-file="https://01010011blog.files.wordpress.com/2023/12/image.png?w=300" data-large-file="https://01010011blog.files.wordpress.com/2023/12/image.png?w=676" width="686" height="386" src="https://01010011blog.files.wordpress.com/2023/12/image.png?w=686" alt="" sizes="(max-width: 686px) 100vw, 686px"></figure>



<p>미라클 글쓰기이므로 부담 가지 않게, 두서 없더라도, 짧은 내용을 휘갈기듯 써볼 생각임.</p>



<p>Typescript에는 PromiseLike라는 interface가 있다.</p>


<div><pre title="">interface PromiseLike&lt;T&gt; {
    /**
     * Attaches callbacks for the resolution and/or rejection of the Promise.
     * @param onfulfilled The callback to execute when the Promise is resolved.
     * @param onrejected The callback to execute when the Promise is rejected.
     * @returns A Promise for the completion of which ever callback is executed.
     */
    then&lt;TResult1 = T, TResult2 = never&gt;(
        onfulfilled?:
            ((value: T) =&gt; TResult1 | PromiseLike&lt;TResult1&gt;) |
            undefined |
            null,
        onrejected?:
            ((reason: any) =&gt; TResult2 | PromiseLike&lt;TResult2&gt;) |
            undefined |
            null
    ): PromiseLike&lt;TResult1 | TResult2&gt;;
}
</pre></div>


<p>Promise와의 차이점은 catch 와 finally 가 존재하지 않는다는 것이다.</p>


<div><pre title="">interface Promise&lt;T&gt; {
    /**
     * Attaches callbacks for the resolution and/or rejection of the Promise.
     * @param onfulfilled The callback to execute when the Promise is resolved.
     * @param onrejected The callback to execute when the Promise is rejected.
     * @returns A Promise for the completion of which ever callback is executed.
     */
    then&lt;TResult1 = T, TResult2 = never&gt;(
        onfulfilled?: 
            ((value: T) =&gt; TResult1 | PromiseLike&lt;TResult1&gt;) | 
            undefined | 
            null, 
        onrejected?: 
            ((reason: any) =&gt; TResult2 | PromiseLike&lt;TResult2&gt;) | 
            undefined | 
            null
    ): Promise&lt;TResult1 | TResult2&gt;;

    /**
     * Attaches a callback for only the rejection of the Promise.
     * @param onrejected The callback to execute when the Promise is rejected.
     * @returns A Promise for the completion of the callback.
     */
    catch&lt;TResult = never&gt;(
        onrejected?: 
            ((reason: any) =&gt; TResult | PromiseLike&lt;TResult&gt;) | 
            undefined | 
            null
    ): Promise&lt;T | TResult&gt;;
}
</pre></div>

<div><pre title="">interface Promise&lt;T&gt; {
    /**
     * Attaches a callback that is invoked when the Promise is settled (fulfilled or rejected). The
     * resolved value cannot be modified from the callback.
     * @param onfinally The callback to execute when the Promise is settled (fulfilled or rejected).
     * @returns A Promise for the completion of the callback.
     */
    finally(onfinally?: (() =&gt; void) | undefined | null): Promise&lt;T&gt;;
}
</pre></div>


<p>PromiseLike가 처음 등장한 시점은 2015년 Typescript 1.6.0-beta 부터이며, 개념적으로 Thenable과 유사하다.<br>다음 문제들을 해결하는데 사용된다.<br>– Bluebird 나 Deffered 등, 비표준 Promise interface 와의 호환성<br>– Observable 같은 다양한 시나리오를 지닌 비동기 객체의 Promise 변환</p>



<p>특히 error 처리 시나리오의 경우, Promise는 catch 에 진입하면 회복 불가능한 반면<br>Observable은 catchError, retry, retryWhen 등 다양한 시나리오가 존재한다.<br>이는 표준 Promise interface로는 처리하기 까다로운 면이 있기에 <br>PromiseLike 같은 최소한의 Thenable 인터페이스로 어설픈 변환을 하는 편이 낫다.</p>
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01010011

침착맨의 미라클 방송을 본받아 미라클 블로그 글쓰기를 해볼까 한다.
미라클 글쓰기이므로 부담 가지 않게, 두서 없더라도, 짧은 내용을 휘갈기듯 써볼 생각임.
Typescript에는 PromiseLike라는 interface가 있다.
interface PromiseLike<T> {
    /**
     * Attaches callbacks for the resolution and/or rejection of the Promise.
     * @param onfulfilled The callback to execute when the Promise is resolved.
     * @param onrejected The callback to execute when the Promise is rejected.
     * @returns A Promise for the completion of which ever callback is executed.
     */
    then<TResult1 = T, TResult2 = never>(
        onfulfilled?:
            ((value: T) => TResult1 | PromiseLike<TResult1>) |
            undefined |
            null,
        onrejected?:
            ((reason: any) => TResult2 | PromiseLike<TResult2>) |
            undefined |
            null
    ): PromiseLike<TResult1 | TResult2>;
}
Promise와의 차이점은 catch 와 finally 가 존재하지 않는다는 것이다.
interface Promise<T> {
    /**
     * Attaches callbacks for the resolution and/or rejection of the Promise.
     * @param onfulfilled The callback to execute when the Promise is resolved.
     * @param onrejected The callback to execute when the Promise is rejected.
     * @returns A Promise for the completion of which ever callback is executed.
     */
    then<TResult1 = T, TResult2 = never>(
        onfulfilled?: 
            ((value: T) => TResult1 | PromiseLike<TResult1>) | 
            undefined | 
            null, 
        onrejected?: 
            ((reason: any) => TResult2 | PromiseLike<TResult2>) | 
            undefined | 
            null
    ): Promise<TResult1 | TResult2>;
    /**
     * Attaches a callback for only the rejection of the Promise.
     * @param onrejected The callback to execute when the Promise is rejected.
     * @returns A Promise for the completion of the callback.
     */
    catch<TResult = never>(
        onrejected?: 
            ((reason: any) => TResult | PromiseLike<TResult>) | 
            undefined | 
            null
    ): Promise<T | TResult>;
}
interface Promise<T> {
    /**
     * Attaches a callback that is invoked when the Promise is settled (fulfilled or rejected). The
     * resolved value cannot be modified from the callback.
     * @param onfinally The callback to execute when the Promise is settled (fulfilled or rejected).
     * @returns A Promise for the completion of the callback.
     */
    finally(onfinally?: (() => void) | undefined | null): Promise<T>;
}
PromiseLike가 처음 등장한 시점은 2015년 Typescript 1.6.0-beta 부터이며, 개념적으로 Thenable과 유사하다.
다음 문제들을 해결하는데 사용된다.
– Bluebird 나 Deffered 등, 비표준 Promise interface 와의 호환성
– Observable 같은 다양한 시나리오를 지닌 비동기 객체의 Promise 변환
특히 error 처리 시나리오의 경우, Promise는 catch 에 진입하면 회복 불가능한 반면
Observable은 catchError, retry, retryWhen 등 다양한 시나리오가 존재한다.
이는 표준 Promise interface로는 처리하기 까다로운 면이 있기에 
PromiseLike 같은 최소한의 Thenable 인터페이스로 어설픈 변환을 하는 편이 낫다.

I am 약속좋아. Promise vs PromiseLike 의 차이점

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