What is the procedure for modifying two consecutive values in an array based on a specific condition?

Question

What is the procedure for modifying two consecutive values in an array based on a specific condition?

I am attempting to insert a dash between even numbers in an array taken from an input. My approach involves using the reduce() method combined with a specific condition that compares two consecutive iterations. Since I am new to programming, it would be great if the solution is simple and easy to understand for me... :)

Although I realize this code snippet does not work as intended, the idea is clear. For example, when given "12534487" as input, I would like the output to be "12534-4-87".


          ar = prompt("numberInput").split("");
          ar.map(x => parseInt(x));
          ar.addDashToEven();
          const addDashToEven = (a, b) => {
            for (a % 2 == 0 && b % 2 == 0) {
              a = a + "-"
            }
          }

javascript arrays

Answer 1

Answer №1

To convert a string into a new string with certain criteria applied, you can split and map through the characters of the string while checking conditions like whether the previous character is even or odd.

In this method, a destructuring assignment is used to access the index of the current character along with a variable representing the previous character.

{ [i - 1]: l }

var string = '124568',
    result = string
        .split('')
        .map((r, i, { [i - 1]: l }) => (l % 2 === 0 && r % 2 === 0 ? '-' : '') + r)
        .join('');

console.log(result);

Answer 2

To convert a string into a new string with certain criteria applied, you can split and map through the characters of the string while checking conditions like whether the previous character is even or odd.

In this method, a destructuring assignment is used to access the index of the current character along with a variable representing the previous character.

{ [i - 1]: l }

var string = '124568',
    result = string
        .split('')
        .map((r, i, { [i - 1]: l }) => (l % 2 === 0 && r % 2 === 0 ? '-' : '') + r)
        .join('');

console.log(result);

Answer 3

Answer №2

Try solving this without using any built-in array methods.

const numString = "12534487";
const numArr = numString.split('');

for(let j = 0; j < numArr.length; j++){
  if(numArr[j] % 2 === 0 && numArr[j+1] % 2 === 0){
    numArr[j] = numArr[j] + '-';   
  }
}

console.log(numArr.join(''))

Answer 4

Try solving this without using any built-in array methods.

const numString = "12534487";
const numArr = numString.split('');

for(let j = 0; j < numArr.length; j++){
  if(numArr[j] % 2 === 0 && numArr[j+1] % 2 === 0){
    numArr[j] = numArr[j] + '-';   
  }
}

console.log(numArr.join(''))

Answer 5

Answer №3

You were so close! To access the previous value, simply add parameters to your map function such as index and originalArray.

console.log(
  "12534487".split("")
  .map((val, index, originalArray) => {
    const prev = originalArray[index - 1];
    return prev !== undefined && !(val % 2) && !(prev % 2) ? "-"+val : val;
  })
  .join("")
)

Alternatively, you can use regular expressions for a more intuitive solution:

console.log(
  "125343424324443487".replace(/([02468])(?=[02468])/g, '$1-')
)

Answer 6

You were so close! To access the previous value, simply add parameters to your map function such as index and originalArray.

console.log(
  "12534487".split("")
  .map((val, index, originalArray) => {
    const prev = originalArray[index - 1];
    return prev !== undefined && !(val % 2) && !(prev % 2) ? "-"+val : val;
  })
  .join("")
)

Alternatively, you can use regular expressions for a more intuitive solution:

console.log(
  "125343424324443487".replace(/([02468])(?=[02468])/g, '$1-')
)

Answer 7

Answer №4

To implement the use of reduce, follow this example:

const numbers = [1, 2, 3, 4, 4, 4, 5, 6, 6, 9];

const result = numbers.reduce((accumulator, currentValue) => {
  if ((accumulator[accumulator.length - 1] % 2 == 0 || typeof accumulator[accumulator.length - 1] === "string") && currentValue % 2 == 0) {
    accumulator[accumulator.length - 1] += "-" + currentValue;
    return accumulator;
  } else {
    accumulator.push(currentValue);
    return accumulator;
  }
}, []);

console.log(result);

Answer 8

To implement the use of reduce, follow this example:

const numbers = [1, 2, 3, 4, 4, 4, 5, 6, 6, 9];

const result = numbers.reduce((accumulator, currentValue) => {
  if ((accumulator[accumulator.length - 1] % 2 == 0 || typeof accumulator[accumulator.length - 1] === "string") && currentValue % 2 == 0) {
    accumulator[accumulator.length - 1] += "-" + currentValue;
    return accumulator;
  } else {
    accumulator.push(currentValue);
    return accumulator;
  }
}, []);

console.log(result);

What is the procedure for modifying two consecutive values in an array based on a specific condition?

Answer №1

Answer №2

Answer №3

Answer №4

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