Here is the link to codesandbox, in case you want to try this out yourself. If that's not the case, sticking with forEach wouldn't be a bad choice. But one distinct advantage of the for loop is its ability to exit a loop early if necessary. So far, weve essentially only highlighted examples in favor of the forEach() method. Map should be used at places where you would need to return some data based on each async operation. The forEach method in Javascript iterates over the elements of an array and calls the provided function for each element in order. This method uses a callback function and applies it to each element in the array, meaning we dont need to use a bracket notation to get each element. while - loops through a block of code while a specified condition is true. for/of - loops through the values of an iterable object. for/in - loops through the properties of an object. Inside the Promise. We use Promise.all to wait for all the promises returned by doSomethingAsync to complete before moving on to the next line of code. When you return, you skip the rest of the forEach() callback and JavaScript goes on to the next iteration of the loop. It should be noted that the Promise.all will reject completely if even a single one of the promises from the input array rejects. JavaScript supports different kinds of loops: for - loops through a block of code a number of times. Working : The main function is marked as async, which means it returns a promise. For practical purposes, return in a forEach() callback is equivalent to continue in a conventional for loop. Later we can do a await Promise.all(promises) to get the final answer array from it. map returns an array of promises, (one promise per execution, in the same order). It allows you to iterate through each item of a given list and do. The map function behaves exactly the same as forEach in terms of async operations, meaning all of the callbacks start at the same time and log exactly after 2 seconds. For Each loops are the most common type of loop used in building backend projects. a simple old-fashioned for loop - async-friendlyįor (let index = 0 index forEach (ES5+ only spec | MDN) (or its relatives some and such) - not async-friendly (but see details) The forEach method in Javascript iterates over the elements of an array and calls the provided function for each element in order.It starts with the first item in the array (. a for-of loop (ES2015+ only spec | MDN) - simple and async-friendly It will loop through the collection and each time through the loop it will use the next item from the collection.
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