Add Two Promises

To solve this coding challenge, you need to work with promises and asynchronously obtain their resolved values to perform an addition. Since promises are fundamental constructs in asynchronous programming, particularly in JavaScript, the goal is to create a new promise that resolves to the sum of the values resolved by two input promises.

Explanation

  1. Understanding Promises:
    • A promise in JavaScript is an object representing the eventual completion or failure of an asynchronous operation.
    • The
      .then()
      method is used to handle the resolved value of a promise.
    • The
      await
      keyword, used in an
      async
      function, pauses the execution of the function until the promise resolves.
  2. The Task:
    • You are given two promises (
      promise1
      and
      promise2
      ), each resolving to a number.
    • The goal is to return a new promise that resolves to the sum of these two numbers.
  3. Asynchronous Addition:
    • Use
      Promise.all()
      to handle multiple promises concurrently and wait until all are resolved. This is efficient and ensures that both promises have resolved before proceeding.
  4. Pseudocode Details:
    • Define an
      async
      function that receives two promises as arguments.
    • Use
      await
      to obtain the resolved values of these promises.
    • Return a new promise that resolves to the sum of these values.

    Detailed Steps in Pseudocode

  5. Define an Asynchronous Function:
    • This function will accept two promises as inputs.
  6. Await Both Promises:
    • Use the
      await
      keyword to get the resolved values of the promises.
  7. Sum the Values:
    • Add the resolved values of the promises.
  8. Return a New Promise:
    • Create and return a new promise that resolves with the sum of the values.

    Pseudocode with Comments

                                                
# Define an asynchronous function called addTwoPromises that accepts two promises.
async function addTwoPromises(promise1, promise2):
# Use await to get the resolved value of promise1
value1 = await promise1

# Use await to get the resolved value of promise2
value2 = await promise2

# Calculate the sum of the resolved values from both promises
sum = value1 + value2

# Return a new promise that resolves with the sum
return sum
    Alternatively, if you want to handle the case where the new promise resolves using
    Promise.all
    , here's another approach: 
                                                
# Define a function to add two promises with concurrent resolution
function addTwoPromises(promise1, promise2):
# Use Promise.all to handle both promises concurrently
return Promise.all([promise1, promise2]).then(function(values):
# Extract the values resolved by promise1 and promise2
value1 = values[0]
value2 = values[1]

# Calculate the sum of the values
sum = value1 + value2

# Return the sum as the resolved value of the new promise
return sum
)

    Comprehensive Explanation of Pseudocode

  9. Defining the Asynchronous Function:
    • The function
      addTwoPromises
      is defined to be
      async
      , which allows the use of
      await
      within it. This ensures the function will pause until each promise resolves.
  10. Using Await to Get Resolved Values:
    • By calling
      await
      on
      promise1
      and
      promise2
      , the code effectively waits for each promise to fulfill and provides their resulting values (
      value1
      and
      value2
      ).
  11. Calculating the Sum:
    • Once both values are available, they are added together to compute the sum.
  12. Returning a New Promise:
    • The final sum is returned, which automatically resolves as a new promise when the function is called.
  13. Alternative Approach Using Promise.all:
    • Using
      Promise.all([promise1, promise2])
      is an efficient way to handle both promises concurrently. This method returns a single promise that is resolved when all the included promises (in this case two) have resolved.
    • The
      then
      block receives an array of the resolved values, sums them, and returns the result as the resolved value of the new promise.
By following these steps, you ensure that both input promises are properly awaited and their results summed, meeting the requirements of the coding challenge while adhering to best practices for handling asynchronous operations.