JavaScript承诺使用setTimeout解决 [英] JavaScript promise resolving with setTimeout

问题描述

我不明白为什么第一个setTimeout函数起作用，而第二个函数不起作用。当我运行第二个setTimeout时，第一个被注释掉。

I don't understand why the first setTimeout function works but the second one doesn't. The first one is commented out when I run the second setTimeout. But instead of resolving after 3 seconds it resolves immediately.

我对整个承诺事物是陌生的，而我正在研究的教程使用setTimeout a的promise

I'm new to the whole 'promise' thing and the tutorial I'm working through uses promises with setTimeout a lot.

  let promise = new Promise( ( resolve, reject ) => {

     /* why does setTimeout work with this one... */
     setTimeout( () => resolve( 'Job\'s done!!!' ), 3000 );

     /* but not with this one */
     setTimeout( resolve('done'), 3000 );
  } );

  promise.then(
     result => alert( result )
  );

推荐答案

/* why does setTimeout work with this one... */
 setTimeout( () => resolve( 'Job\'s done!!!' ), 3000 );

发生超时时，您调用函数（）=> ... 直到执行完成为止

when the timeout occur you call a function () => ... wich when executed till resolve the promise

/* but not with this one */
 setTimeout( resolve('done'), 3000 );

在这里，您实际解决了promise（执行result函数）并将结果传递给setTimeout函数

here you actually resolve the promise (you execute the result function) and pass the result to the setTimeout function.

写作

() => resolve( 'Job\'s done!!!' )

与

is the same as

function() {
    resolve( 'Job\'s done!!!' );
}

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