Need help on thinking about how to solve my problem

Question

I want to replace my for loop by higher order functions in my problem.

I need to create a function that takes an array as parameter and return an array with the values of the input array that match x, let's say 10.

For exemple

const matchesValues = ( array ) => {
    //MyFunc
} 
console.log(matchesValues([2,8,5,5,6])) // [[2,8], [5,5]]

Here is what I have done for the moment:

 const matchesValues = (array) => { if (array.length > 1) { const matches = [] for (let i = array.length - 1; i >= 0; i--) { if (i - 1 >= 0) { if (array[i] + array[i - 1] == 10) { matches.push([array[i - 1], array[i]]) } } } return matches } } console.log(matchesValues([2,8,5,5,5,6])) // expected: [2,8,5,5], recieved: [[5,5], [5,5], [2,8]]

Note that the order would stay the same, but this I can handle.

By which higher order function(s) would you replace my forloop?

Thanks a lot for your time.

Answer 1

Use reduce

 const matchesValues = ( array ) => { return array.reduce((previousValue, currentValue, currentIndex) => { if (currentIndex === 0 || (array[currentIndex - 1] + currentValue) === 10) { previousValue.push(currentValue); } return previousValue; }, []); }; console.log(matchesValues([2,8,5,5,5,6]));

Answer 2

there is a longer solution here but with the same return result format [[2,8], [5,5]] what you requested. Also it handles the case when there is only 1 value that matches up the sum , eg: 10 .

const matchValues = (array, valueToMatch) => {
  const matchingValues = [];
  if(!array.length) {
      return matchingValues;
  }
  array.forEach((actualValue, index) => {
     if((array.length-1) === index) {
         if(actualValue === valueToMatch) {
            matchingValues.push([actualValue]);
         }
     }
     const clonedArray = array.filter((_, clonedValueIndex) => clonedValueIndex !== index);
     clonedArray.forEach((value) => {
       if((value + actualValue) === valueToMatch) {
         let alreadyMatched = false;
         if(matchingValues.length) {
           matchingValues.forEach((matchingValue) => {
             if(matchingValue.includes(value) && matchingValue.includes(actualValue) && (value + actualValue === valueToMatch)) {
              alreadyMatched = true;
             }
           })
         }
         if(!alreadyMatched) {
          matchingValues.push([actualValue, value]);
         }
       }
     })
  });
  return matchingValues;
}

const returnedMatchingvalues = matchValues([2,8,5,5,5,6,10], 10);
console.log(returnedMatchingvalues); // [ [ 2, 8 ], [ 5, 5 ], [ 10 ] ]