TypeScript combine multiple Promises await-CodePudding

I have basically a piece of code where I have a variable that consolidates multiple promise awaits and concat them into a single object

const traversals = (await traverseSchemas({filename:"my-validation-schema.json"}).concat([
      _.zipObject(
        ["id-1", "id-2"],
        [
          await loadSchema({
            filename: "schema-1.json"
          }),
          await loadSchema({
            filename: "schema-2.json"
          }),
        ]
      ),
    ]);

The traverseSchemas returns an array object [{"key1":{object}}, {"key2": {object}}]

I am exploring if there is a away I can apply await at traversals level only to get all the promised fulfilled data or if there is any better way to refactor the code.

CodePudding user response：

Because no promise depends on the result of another, you can execute all of them simultaneously (in parallel) using Promise.all. This only utilizes a single await and the return ... is a purely synchronous expression combining the awaited values -

async function traversals() {
  const [validation, schema1, schema2] = await Promise.all([
    traverseSchemas({filename:"my-validation-schema.json"}),
    loadSchema({filename: "schema-1.json"}),
    loadSchema({filename: "schema-2.json"}),
  ])

  return [
    ...validation,
    _.zipObject(["id-1", "id-2"], [schema1, schema2])
  ]
}

If you have access to top-level await or this is already part of another async function, you can define const traversals = ... instead of using return -

const [validation, schema1, schema2] = await Promise.all([
  traverseSchemas({filename:"my-validation-schema.json"}),
  loadSchema({filename: "schema-1.json"}),
  loadSchema({filename: "schema-2.json"}),
])

const traversals = [
  ...validation,
  _.zipObject(["id-1", "id-2"], [schema1, schema2])
]

CodePudding user response：

There are many options.

Typically plain code is easier to understand. So I would go for something like this:

const validationSchemas = await traverseSchemas({ filename:"my-validation-schema.json" })
const schema1 = { "id-1": await loadSchema({ filename: "schema1-json" });
const schema2 = { "id-2": await loadSchema({ filename: "schema2-json" });

const traversals = [ ...fetchedSchemas, schema1, schema2 ];

If you want to parallelize awaits, you could prepare them first, then request via Promise.all and then join together:

const tasks = [
    traverseSchemas({ filename:"my-validation-schema.json" }),
    loadSchema({ filename: "schema1-json" }),
    loadSchema({ filename: "schema2-json" })
];

const [validationSchemas, schema1Value, schema2Value] = await Promise.all(tasks);

const traversals = [
    ...validationSchemas,
    { 'id-1': schema1Value },
    { 'id-2': schema2Value }
];