JavaScript Arrays and Callbacks

A promise that resolves once all the promises in the input array are resolved. The resolved values of all promises are returned in an array.

A promise that rejects immediately if any of the promises in the input array rejects, without waiting for the others to resolve.

A method that waits for all promises in the input array to settle (resolve or reject) and returns an array of objects containing the status and value/reason of each promise.

A keyword used to declare a function that will return a promise.

A way to handle promises and asynchronous operations within asynchronous functions. It allows you to pause the execution of a function until a promise resolves or rejects.

The await keyword pauses the execution of an async function until the promise it is waiting for resolves or rejects.

An asynchronous function that uses the await keyword to wait for the result of an asynchronous operation. It returns a resolved promise containing the result of the awaited operation.

A method that handles the resolved value of a promise. It is executed when the promise resolves successfully.

In asynchronous programming, the program doesn't wait for a task to complete before moving on to the next. It allows the program to continue executing while waiting for a task to finish.

The Call Stack is used to store the functions that are currently being executed. The Callback Queue holds functions waiting to be executed once the call stack is empty.

The Web API handles tasks like fetching data from the network or making DOM manipulations. It returns a result to the Callback Queue after completing the task.

A callback function is passed as an argument to another function and is executed when the first function completes its task.

Callback hell is a term used to describe code with deeply nested callback functions. It makes code difficult to read and maintain.

A Promise is an object representing the eventual completion (or failure) of an asynchronous operation, and allows you to handle the outcome.

The resolve function of a Promise is called when the asynchronous operation completes successfully. You can chain actions to be done after a successful result.

The reject function of a Promise is called if the asynchronous operation encounters an error. It allows you to handle potential failures.

The map() method is used to iterate through each element in an array, apply a function to it, and create a new array containing the results. It does not modify the original array.

The filter() method iterates through an array, applying a condition (a function). It returns a new array containing only the elements that satisfy the condition.

The reduce() method iterates through an array, applying a reducer function, which operates on the accumulator and the current element. It returns a single output value.

The reduce() method requires a callback function that takes two parameters: the accumulator and the current element. The accumulator is initialized to the first element of the array.

Asynchronous JavaScript allows code to execute outside of the sequential order it appears in. It means actions can happen simultaneously without blocking the execution flow.

The reduce() method can be used with a specified initial value for the accumulator. If not provided, the first element of the array serves as the initial value.

Async JavaScript allows for non-blocking operations. This means the script can continue executing other tasks while waiting for asynchronous operations to complete.

Examples of asynchronous operations in JavaScript include network requests, file reading, and event handling. These operations may take time and shouldn't block the execution of other code.