Delete a character from a string in JavaScript by targeting a specific position starting from the end

I've been grappling with a problem involving removing a specific character at a known position from the back of a string. Here's the situation:

Currently, I have strings like:

'RX8567' 'A8532' '18256'

I want to delete the first '8' I encounter in each string. However, I would prefer to tackle this issue from the end of the string, as I am uncertain of the number of alphanumeric characters at the beginning. From the back, I know that the character I want to remove will always be the 4th character. So, if the '8' is the fourth character of the string from the end, I want to remove it. I've managed to achieve this from the front with the following code:

    var string = 'A8532'            
    var string = string.slice(0,1) + string.slice(2);

This should result in:

'A532'

However, this only works if the '8' immediately follows the 'A'. Is there an alternate or simpler method of achieving this while working from the back of the string as described? Thank you in advance!

javascript

Answer №1

Here is a suggested solution for the given problem:

var code = 'RX8567';
//if '8' is the fourth character of the string moving from the back remove it
if (code.slice(-4, -3) === '8') {
    code = code.slice(0, -4) + code.slice(-3);
}

code.slice(0, -4) will provide all characters except the last four

code.slice(-3) will give the last three characters

Alternatively, you can use a regular expression for the same task:

var code = 'RX8567';
code = code.replace(/(?:^(.*)8(.{3})$)/, '$1$2');

(?: is used to create a non-capturing group (the entire expression)

^ signifies the start of the string

(.*) matches any number of characters (represented by group $1 in the replacement string)

8 is the specific character '8' to be matched

(.{3}) matches three characters of any kind (represented by group $2 in the replacement string)

$ denotes the end of the string

) closes the bracket for the initial group in the regular expression

For processing a large number of such codes, the first solution may offer significantly improved speed.

Answer №2

Give this a shot:

function eliminateEight(code) {
    let eightPosition = code.indexOf('8');
    return eightPosition === -1 ? code : code.slice(0, eightPosition) + code.slice(eightPosition + 1);
};

let codes = ['RX8567', 'A8532', '18256'];

for (let i = 0; i < codes.length; ++i) {
    console.log(codes[i] + ' transforms into ' + eliminateEight(codes[i]));
}

Answer №3

function removeEight(value){

  // Grab the 4th character from the end of the string
  var char4 = value.charAt(value.length - 4);
  
  // If the character is '8', remove it from the string
  value =  char4 === '8' ? value.replace(value[value.length - 4], '') : value;
  console.log(value);
}

removeEight('RX8567');
removeEight('A9532');
removeEight('18258');

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