Eliminating blank elements from arrays using JavaScript

Question

Eliminating blank elements from arrays using JavaScript

I'm looking for some assistance in deciphering the functionality of my code. I'm trying to create a function that will take a string as input and eliminate all letters, leaving only numbers behind. The goal is to have this function return an array containing all the numbers extracted from the string. With help from stackoverflow, I've managed to come up with the following:

number = "32321FDFDS 44"
arr = number.replace(/[A-Za-z]/g," ").split(" ")

for(var i = arr.length - 1; i >= 0; i--){
     if(arr[i] == "") {
          arr.splice(i, 1);
    }
}

As a result, I get

[ '32321', '44' ]

This output works well for me at the moment. However, I'm puzzled by how arr.splice(i,1) manages to remove empty strings. It doesn't seem logical that it has this effect on the contents of arr. Can someone provide clarification on this?

javascript arrays string

Answer 1

Answer №1

Example :

if (arr[n] == "") // if the element at index `n` in array `arr` is equal to `""`, then do something

Check out Array.prototype.splice()

Illustrating with a two-item array :

var arr = ["123", ""];
if (arr[0] == "") {
  arr.splice(0,1);
} else {
  console.log(arr); // ["123", ""]
};
if (arr[1] == "") {
  arr.splice(1,1);
  console.log(arr); // ["123"]
};

Answer 2

Example :

if (arr[n] == "") // if the element at index `n` in array `arr` is equal to `""`, then do something

Check out Array.prototype.splice()

Illustrating with a two-item array :

var arr = ["123", ""];
if (arr[0] == "") {
  arr.splice(0,1);
} else {
  console.log(arr); // ["123", ""]
};
if (arr[1] == "") {
  arr.splice(1,1);
  console.log(arr); // ["123"]
};

Answer 3

Answer №2

Contrary to other techniques that produce a fresh array while leaving the original unchanged, the .splice method alters an array by directly modifying it.

When you see the statement arr.splice(i, 1);, it means that starting from index i, one element is removed from array arr. Similarly, if(arr[i] == "") indicates that if the element at index i is an empty string, execute the code inside this conditional block. Consequently, when the condition in the if statement evaluates to true, the corresponding item gets deleted from the array.

Unless you have a specific need to cater to ES3-compatible browsers (like IE8 or older), instead of iterating through the array as shown, consider utilizing the .filter method:

var number = "32321FDFDS 44",
  arr = number.replace(/[A-Za-z]/g," ").split(" ").filter(function (item) {
    return !!item; // all strings except an empty string will coerce to true
  });

console.log(arr);

jsFiddle

If your objective is simply to extract numeric strings from a given string without any additional conditions, a more concise approach would be to split based on one or more non-numeric characters:

var number = "32321FDFDS 44",
  arr = number.split(/\D+/);

// final array contains [ "32321", "44" ]
console.log(arr);

This single-step process eliminates the need to filter out empty strings altogether.

Answer 4

Contrary to other techniques that produce a fresh array while leaving the original unchanged, the .splice method alters an array by directly modifying it.

When you see the statement arr.splice(i, 1);, it means that starting from index i, one element is removed from array arr. Similarly, if(arr[i] == "") indicates that if the element at index i is an empty string, execute the code inside this conditional block. Consequently, when the condition in the if statement evaluates to true, the corresponding item gets deleted from the array.

Unless you have a specific need to cater to ES3-compatible browsers (like IE8 or older), instead of iterating through the array as shown, consider utilizing the .filter method:

var number = "32321FDFDS 44",
  arr = number.replace(/[A-Za-z]/g," ").split(" ").filter(function (item) {
    return !!item; // all strings except an empty string will coerce to true
  });

console.log(arr);

jsFiddle

If your objective is simply to extract numeric strings from a given string without any additional conditions, a more concise approach would be to split based on one or more non-numeric characters:

var number = "32321FDFDS 44",
  arr = number.split(/\D+/);

// final array contains [ "32321", "44" ]
console.log(arr);

This single-step process eliminates the need to filter out empty strings altogether.

Eliminating blank elements from arrays using JavaScript

Answer №1

Answer №2

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