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如何避免Promise.all的承诺构造函数反模式

更新时间:2023-10-30 16:19:34

你可以把新的承诺一起摆脱。

  getFoo = function(){
var promises = [];
promises.push(getBar1()。then(function(bar1){
processBar1(bar1);
return bar1;
}));
promises.push(getBar2()。then(function(bar2){
processBar2(bar2);
return bar2;
}));
return Promise.all(promises).spread(function(bar1,bar2){
var result = processBothBars(bar1,bar2);
return result;
});
}

  // start mockfunction getBar1 (){return Promise.resolve({name:'bar1',processed:false});} function getBar2(){return Promise.resolve({name:'bar2',processed:false});} function processBar1(bar1 ){bar1.processed = true;} function processBar2(bar2){bar2.processed = true;} function processBothBars(bar1,bar2){return [bar1,bar2] .filter(function(bar){return bar.processed;} ).map(function(bar){return bar.name;});} Promise.prototype.spread = function(fn){return this.then(function(arr){return fn.apply(this,arr);} );}; // end mockvar getFoo = function(fail){var promises = []; promises.push(getBar1()。then(function(bar1){processBar1(bar1); if(fail){throw'getBar1 Failed!';} return bar1;})); promises.push(getBar2()。then(function(bar2){processBar2(bar2); return bar2;}));返回Promise.all(promises).spread(function(bar1,bar2){var result = processBothBars(bar1,bar2); return result;});} getFoo()然后(function(result){console.log ); // ['bar1','bar2']}); getFoo(true).then(function(result){console.log(result); //不会发生})catch(function(e) {console.error(e); //错误:getBar1 Failed!});  



.then 返回承诺,所以没有必要创建一个包装它的新的,除非你想防止错误达到外部承诺。 p>

How do you avoid the promise constructor antipattern when using multiple promises and Promise.all?

Say I have the following code:

getFoo = function() {
    return new Promise(function(resolve, reject) {
        var promises = [];
        promises.push(new Promise(function(resolve, reject) => {
            getBar1().then(function(bar1) {
                processBar1(bar1); 
                resolve(bar1);
            });
        }));
        promises.push(new Promise(function(resolve, reject) => {
            getBar2().then(function(bar2) {
                processBar2(bar2); 
                resolve(bar2);
            });
        }));
        Promise.all(promises).spread(function(bar1, bar2) {
            var result = processBothBars(bar1, bar2);
            resolve(result);
        });
    });
}

It presents some of the fundamental issues of the antipattern, errors get swallowed up, and pyramids of doom.

I am using bluebird BTW.

You can just get rid of new Promise all together.

getFoo = function() {
    var promises = [];
    promises.push(getBar1().then(function(bar1) {
        processBar1(bar1);
        return bar1;
    }));
    promises.push(getBar2().then(function(bar2) {
        processBar2(bar2);
        return bar2;
    }));
    return Promise.all(promises).spread(function(bar1, bar2) {
        var result = processBothBars(bar1, bar2);
        return result;
    });
}

// start mock
function getBar1() {
    return Promise.resolve({name:'bar1',processed: false});
}
function getBar2() {
    return Promise.resolve({name:'bar2',processed: false});
}
function processBar1(bar1) {
  bar1.processed = true;
}
function processBar2(bar2) {
  bar2.processed = true;
}
function processBothBars (bar1, bar2) {
  return [bar1, bar2].filter(function (bar) {
    return bar.processed;
  }).map(function (bar) {
    return bar.name;
  });
}
Promise.prototype.spread = function (fn) {
  return this.then(function (arr) {
      return fn.apply(this, arr);
  });
};
// end mock

var getFoo = function (fail) {
    var promises = [];
    promises.push(getBar1().then(function (bar1) {
        processBar1(bar1);
        if (fail) {
          throw 'getBar1 Failed!';
        }
        return bar1;
    }));
    promises.push(getBar2().then(function (bar2) {
        processBar2(bar2);
        return bar2;
    }));
    return Promise.all(promises).spread(function (bar1, bar2) {
        var result = processBothBars(bar1, bar2);
        return result;
    });
}
getFoo().then(function (result) {
    console.log(result); // ['bar1', 'bar2']
});
getFoo(true).then(function (result) {
    console.log(result); // doesn't happen
}).catch(function (e) {
    console.error(e); // Error: getBar1 Failed!
});

.then returns a promise, so there's no need to create a new one that wraps it unless you want to prevent errors from reaching the outer promise.