Question

我有这种情况，我想知道承诺的状态。下面，函数start仅在someTest不再运行时调用start（Promise未挂起）。可以多次调用false函数，但如果在测试仍在运行时调用它，它将不会等待并仅返回class RunTest { start() { retVal = false; if (!this.promise) { this.promise = this.someTest(); retVal = true; } if ( /* if promise is resolved/rejected or not pending */ ) { this.promise = this.someTest(); retVal = true; } return retVal; } someTest() { return new Promise((resolve, reject) => { // some tests go inhere }); } }

this.promise.isPending

我找不到简单检查承诺状态的方法。像awk '{sub(/_otherinfo/, "", $1); print "NEW_"$1 "\t" $2}' file这样的东西会很好:)任何帮助都会受到赞赏！

Answer 1

您可以附加then处理程序，在承诺（或done实例上设置RunTest标记（如果您愿意），并测试：

     if (!this.promise) {
         this.promise = this.someTest();
         this.promise.catch(() => {}).then(() => { this.promise.done = true; });
         retVal = true;                
     }

     if ( this.promise.done ) {
         this.promise = this.someTest();
         this.promise.catch(() => {}).then(() => { this.promise.done = true; });
         retVal = true;
     }

注意空的catch()处理程序，无论promise的结果如何，都必须调用处理程序。您可能希望将其包装在函数中以保持代码DRY。

Answer 2

class RunTest {
   constructor() {
    this.isRunning = false;
   }
   start() {
      console.log('isrunning', this.isRunning);
      var retVal = false;
      if(!this.isRunning) {
        this.promise = this.someTest();
        this.promise.catch().then(() => { this.isRunning = false; });
        retVal = true;                
      }
      return retVal;
    }
    someTest() {
        this.isRunning = true;
        return new Promise((resolve, reject) => {
          setTimeout(function() {
             //some tests go inhere
             resolve();
           }, 1000);
        });
    }
};

var x = new RunTest();

x.start(); //logs false
x.start(); //logs true

setTimeout(function() {
    //wait for a bit
  x.start(); //logs false
}, 2000);

如何检查Promise是否有待处理

2 个答案: