for-each.md

simple foreach

This example demonstrates a simple for-each (or: for ... of) statement. It converts an array of numbers to a single string. in order to ensure there is no leading , a local variable is used to treat the first element in the array differently. This function returns 1, 2, 3.. Open in playground

export const main = asl.deploy.asStateMachine(async () => {
  const arr = [1, 2, 3];
  let result = "";

  // use a for loop to append all numbers to a single string
  for (const item of arr) {
    if (result === "") {
      //first element should not be prefixed with a comma
      result = asl.convert.numberToString(item);
    } else {
      result = `${result}, ${item}`;
    }
  }
  return result;
});

foreach with break

This example demonstrates a break statement within a for-each statement. The break statements exists the loop after number 2 was added to the list. this function returns 1, 2. Open in playground

export const main = asl.deploy.asStateMachine(async () => {
  const arr = [1, 2, 3];
  let result = "";

  // use a for loop to append all numbers to a single string
  for (const item of arr) {
    if (result === "") {
      //first element should not be prefixed with a comma
      result = asl.convert.numberToString(item);
    } else {
      result = `${result}, ${item}`;
    }
    if (item === 2) {
      break; // this break will prevent 3 from being added to the string
    }
  }
  return result;
});

foreach with continue

This example demonstrates a continue statement within a for-each statement. The continue statements prevents number 2 from being added to the list. this function returns 1, 3. Open in playground

export const main = asl.deploy.asStateMachine(async () => {
  const arr = [1, 2, 3];
  let result = "";
  // use a for loop to append all numbers to a single string
  for (const item of arr) {
    if (item === 2) {
      continue; // this break will prevent 2 from being added to the string
    }
    if (result === "") {
      //first element should not be prefixed with a comma
      result = asl.convert.numberToString(item);
    } else {
      result = `${result}, ${item}`;
    }
  }
  return result; //returns "1, 3"
});

foreach early return

This example demonstrates a return statement within a for-each statement. The return prevents the loop from processing, and the function returns found 2!. Open in playground

export const main = asl.deploy.asStateMachine(async () => {
  const arr = [1, 2, 3];
  for (const item of arr) {
    if (item === 2) {
      return `found ${item}!`; //returns "found 2!"
    }
  }
  throw new Error("should not get here");
});

nested foreach

Open in playground

export const main = asl.deploy.asStateMachine(async () => {
  const numbers = [0, 1, 2, 3];
  const letters = ["a", "b", "c", "d"];
  const global = "prefix";
  const outer = { middle: { inner: 3 } };
  let result = ``;
  for (const number of numbers) {
    for (const letter of letters) {
      const combined = { number, letter, global, inner: outer.middle.inner };
      result = `${result}, ${asl.states.jsonToString(combined)}`;
    }
  }
  return result;
});

empty foreach

Open in playground

export const main = asl.deploy.asStateMachine(async () => {
  const numbers = [0, 1, 2, 3];
  for (const _number of numbers) {
  }
  return "ok";
});