Utilizing API calls within a loop using AngularJS

Question

Utilizing API calls within a loop using AngularJS

I need to execute a series of APIs in a loop, but I want the second loop to start only after receiving the result from the last API call in the first loop. How can I achieve this?

for(var i=0; i<array.length; i++ )
    service.getfunction(array[i]).then(function(response) {
      service.getfunction1(response).then(function(response) {
        service.getfunction2(response).then(function(response) {
          service.getfunction3(response).then(function(response) {
             console.log(response);
          });
        });
      });
    });
)

javascript angularjs api for-loop promise

Answer 1

Answer №1

To start, you have the ability to chain promises together in the following manner:

function performTask(index) {
  return service.fetchData(array[index]).then(function(data) {
    return service.processData1(data);
  }).then(function(result) {
    return service.processData2(result);
  }).then(function(finalResult) {
    return service.processData3(finalResult);
  }).then(function(response) {
    console.log(response);
  });
}

This function will produce a promise that resolves once all necessary service calls are completed. Now let's put it into action:

var promise = Promise.resolve(true);
for(var index = 0; index < array.length; index++) {
  (function(i) { //It is crucial to wrap it to prevent passing incorrect index value to performTask
    promise = promise.then(function() {
      return performTask(i);
    });
  })(index);
}
promise.then(function() {
  console.log('All tasks finished');
});

Answer 2

To start, you have the ability to chain promises together in the following manner:

function performTask(index) {
  return service.fetchData(array[index]).then(function(data) {
    return service.processData1(data);
  }).then(function(result) {
    return service.processData2(result);
  }).then(function(finalResult) {
    return service.processData3(finalResult);
  }).then(function(response) {
    console.log(response);
  });
}

This function will produce a promise that resolves once all necessary service calls are completed. Now let's put it into action:

var promise = Promise.resolve(true);
for(var index = 0; index < array.length; index++) {
  (function(i) { //It is crucial to wrap it to prevent passing incorrect index value to performTask
    promise = promise.then(function() {
      return performTask(i);
    });
  })(index);
}
promise.then(function() {
  console.log('All tasks finished');
});

Answer 3

Answer №2

Enclose everything within a function:

// Define the wrapping function 
function RepeatAPI() {
    for(var i=0; i<arr.length; i++ )
        serv.getfunc(arr[i]).then(function(resp) {
          serv.getfunc1(resp).then(function(resp1) {
            serv.getFunc2(resp1).then(function(resp2) {
              serv.getfunc3(resp2).then(function(resp3) {
                 console.log(resp3);

                 // Call the function again
                 RepeatAPI();
              });
            });
          });
        });
    )
}

// Initial function call
RepeatAPI();

Answer 4

Enclose everything within a function:

// Define the wrapping function 
function RepeatAPI() {
    for(var i=0; i<arr.length; i++ )
        serv.getfunc(arr[i]).then(function(resp) {
          serv.getfunc1(resp).then(function(resp1) {
            serv.getFunc2(resp1).then(function(resp2) {
              serv.getfunc3(resp2).then(function(resp3) {
                 console.log(resp3);

                 // Call the function again
                 RepeatAPI();
              });
            });
          });
        });
    )
}

// Initial function call
RepeatAPI();

Answer 5

Answer №3

To execute a chain of promises sequentially, you can utilize Array.reduce along with the .then() method as demonstrated below:

array.reduce(function(previous, next)
{
    return previous.then(function()
    {
        return service.getFirstFunction(next);
    })
    .then(function(response)
    {
        return service.getSecondFunction(response);
    })
    .then(function(response)
    {
        return service.getThirdFunction(response);
    })
    .then(function(response)
    {
        return service.getFourthFunction(response);
    });
}, Promise.resolve())
.then(function()
{
    console.log("All tasks completed successfully.");
})
.catch(function(error)
{
    console.log(error);
});

Answer 6

To execute a chain of promises sequentially, you can utilize Array.reduce along with the .then() method as demonstrated below:

array.reduce(function(previous, next)
{
    return previous.then(function()
    {
        return service.getFirstFunction(next);
    })
    .then(function(response)
    {
        return service.getSecondFunction(response);
    })
    .then(function(response)
    {
        return service.getThirdFunction(response);
    })
    .then(function(response)
    {
        return service.getFourthFunction(response);
    });
}, Promise.resolve())
.then(function()
{
    console.log("All tasks completed successfully.");
})
.catch(function(error)
{
    console.log(error);
});

Utilizing API calls within a loop using AngularJS

Answer №1

Answer №2

Answer №3

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