How can I filter out strings and only keep the numbers in an array using JavaScript?

Question

How can I filter out strings and only keep the numbers in an array using JavaScript?

After searching through numerous similar questions, I have been unable to find a solution to this particular challenge. I am in need of a function that can remove all non-number items from an array while also modifying the existing array rather than creating a new one. My attempt so far looks like this:

 let array = [1, 'a', 'b', 2];
 array = array.filter(item => typeof item !== "string");
 console.log(array);

 //--> [1, 2]

While this code gives me the desired output, it falls short on some additional requirements. According to MDN, the result creates a new array with the filtered values, which I did not fully consider.

If anyone has more experience in solving this kind of problem, I would greatly appreciate your help. I've spent hours attempting various solutions involving array.splice and for loops, but have not come close to success. Thank you in advance for any assistance, and apologies for the lengthy post.

javascript arrays string integer

Answer 1

Answer №1

If you want to remove elements from an array in a reverse order, you can utilize the Array#splice() method within a backward for loop.

When working backwards, removing elements will not impact the indexes in the forward direction because the original elements are still present from index 0 up to the current position.

let array = [1, 'a', 'b', 2];

for (let i = array.length - 1; i >= 0; i--) {
  if (typeof array[i] === "string") {// adjust condition as needed
    array.splice(i, 1);
  }
}

console.log(array);

//--> [1, 2]

Answer 2

If you want to remove elements from an array in a reverse order, you can utilize the Array#splice() method within a backward for loop.

When working backwards, removing elements will not impact the indexes in the forward direction because the original elements are still present from index 0 up to the current position.

let array = [1, 'a', 'b', 2];

for (let i = array.length - 1; i >= 0; i--) {
  if (typeof array[i] === "string") {// adjust condition as needed
    array.splice(i, 1);
  }
}

console.log(array);

//--> [1, 2]

Answer 3

Answer №2

If you're looking for an alternative approach, consider sorting the array before looping through it. Here's an example:

const array = [1, 'a', 'b', '2', 3, 2]

// sort by type, moving strings to the end
array.sort(a => typeof a === 'string')
// remove the string elements
array.splice(array.findIndex(i => typeof i === 'string'))

console.log(array)

//--> [1, 3, 2]

This method takes advantage of the in-place sorting functionality, specifically targeting strings and removing them efficiently. It adheres to your specified requirements, reduces the risk of loop errors, and only requires one call to splice.

However, have you considered why mutating the original array is necessary? Perhaps using filter would offer a clearer and more readable solution.

Answer 4

If you're looking for an alternative approach, consider sorting the array before looping through it. Here's an example:

const array = [1, 'a', 'b', '2', 3, 2]

// sort by type, moving strings to the end
array.sort(a => typeof a === 'string')
// remove the string elements
array.splice(array.findIndex(i => typeof i === 'string'))

console.log(array)

//--> [1, 3, 2]

This method takes advantage of the in-place sorting functionality, specifically targeting strings and removing them efficiently. It adheres to your specified requirements, reduces the risk of loop errors, and only requires one call to splice.

However, have you considered why mutating the original array is necessary? Perhaps using filter would offer a clearer and more readable solution.

Answer 5

Answer №3

To achieve this, utilize a pointer alongside a `while` loop that verifies whether the pointer has read the end of the array:

let arr = [1, 'a', 'b', 2, 3, 'c', 'd', 3];
let ptr = 0;

while (ptr < arr.length) {
  if (typeof arr[ptr] === "string") arr.splice(ptr, 1);
  else ptr++;
}

console.log(arr);

It's important to note that when we choose to splice an element, we do not increment the pointer.

Answer 6

To achieve this, utilize a pointer alongside a `while` loop that verifies whether the pointer has read the end of the array:

let arr = [1, 'a', 'b', 2, 3, 'c', 'd', 3];
let ptr = 0;

while (ptr < arr.length) {
  if (typeof arr[ptr] === "string") arr.splice(ptr, 1);
  else ptr++;
}

console.log(arr);

It's important to note that when we choose to splice an element, we do not increment the pointer.

Answer 7

Answer №4

If you're looking to clean up an array by removing specific elements, consider using a while loop that iterates from the end of the array and removes elements based on their type with the help of the Array.splice() method.

let arr = [1, 'a', 'b', 2];

let j = arr.length;

while (j--) {
    if (typeof arr[j] === 'string') {
        arr.splice(j, 1);
    }
}

console.log(arr);

Answer 8

If you're looking to clean up an array by removing specific elements, consider using a while loop that iterates from the end of the array and removes elements based on their type with the help of the Array.splice() method.

let arr = [1, 'a', 'b', 2];

let j = arr.length;

while (j--) {
    if (typeof arr[j] === 'string') {
        arr.splice(j, 1);
    }
}

console.log(arr);

How can I filter out strings and only keep the numbers in an array using JavaScript?

Answer №1

Answer №2

Answer №3

Answer №4

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