When to Use the Promise.all() Method
Explore how to use Promise.all() to wait for multiple promises to fulfill or fail together. Understand common scenarios like reading files in parallel, calling multiple web service APIs simultaneously, and introducing artificial delays in browser-based applications. This lesson helps you manage multiple asynchronous operations where any failure should stop the entire process.
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We want to use Promise.all() in any situation where we are waiting for multiple promises to fulfill and any one failure could cause the entire operation to fail. Here are some common use cases for Promise.all().
Processing multiple files together
When using a server-side JavaScript runtime, such as Node.js or Deno, we may need to read from multiple files to work with data contained inside. In this situation, it’s most efficient to read files in parallel and wait until they’ve all been read before proceeding to process the data we’ve retrieved. Here’s an example that works in Node.js:
{
"fruit": "Pear",
"size": "Medium",
"color": "Green"
}This example uses the Node.js promises-based file system API to read multiple files in parallel. The readFiles() function accepts an array of file names to read and then maps each file name to a promise created by the imported readFile() function. The file is read as text (as indicated by the utf8 encoding passed as the second argument), and the results are available in the fulfillment ...