重构 JavaScript ES6

Question

i need help with refactoring below block of code. I was asked to avoid using let and to use const, how can i use constant here as i need to return all the options having possible match id.

    const findRecordExists = (options, possibleMatchId) => {
  let item;
  options.forEach(option => {
    option.waivers.forEach(waiver => {
      if (waiver.waiverNameId === possibleMatchId) {
        item = option;
      }
    });
  });
  return item;
};

Example of options would be :

options: [{
  name:Abc
  waivers: [ {waiverNameId :1}, {waiverNameId:2} ]
}]

Answer 1

Use filter to iterate over the options array, returning whether .some of the waiverNameId s match:

const findRecordExists = (options, possibleMatchId) => {
  return options.filter(
    ({ waivers }) => waivers.some(
      ({ waiverNameId  }) => waiverNameId === possibleMatchId
    )
  );
};

Or, if you don't like destructuring:

const findRecordExists = (options, possibleMatchId) => {
  return options.filter(
    option => option.waivers.some(
      wavier => wavier.waiverNameId => waiverNameId === possibleMatchId
    )
  );
};

Since the result is being immediately returned from the findRecordExists function, there isn't even any need for an intermediate item (or items ) variable.

Answer 2

That's okay.

Using const to declare an identifier only makes the value of the identifier unchangeable if the value of the identifier is a JavaScript primitive eg a number or a boolean.

If the value of the identifier is an object or an array (an array is a type of object in JavaScript), using const to declare it doesn't mean that the value of that object identifier cannot be changes. It only means that the identifier cannot be reassigned.

To refactor your code using const , use the code listing below

const findRecordExists = (options, possibleMatchId) => {
  const optionsWithPossibleMatches = [];
  options.forEach(option => {
    option.waivers.forEach(waiver => {
      if (waiver.waiverNameId === possibleMatchId) {
        optionsWithPossibleMatches.push(option);
      }
    });
  });
  return optionsWithPossibleMatches;
};

If you want to skip intermediate steps of creating variables to store each option that matches your condition, you can use the filter method as prescribed by @CertainPerformance

Answer 3

You can re-factor with using find method. This will simplify and avoids the item variable.

 const options = [ { name: "Abc", waivers: [{ waiverNameId: 1 }, { waiverNameId: 2 }] } ]; const findRecordExists = (options, possibleMatchId) => options.find(option => option.waivers.find(waiver => waiver.waiverNameId === possibleMatchId) ); console.log(findRecordExists(options, 2)); console.log(findRecordExists(options, 3));