Is there a way to trim the string after the second occurrence of an underscore?

Question

Is there a way to trim the string after the second occurrence of an underscore?

I am faced with the task of extracting file names and types from a list of files in an object and displaying them in a table. The list of files is returned by the server in the format: timestamp_id_filename.

For example:

1568223848_12345678_some_document.pdf

To achieve this, I created a helper function that processes the string.

Initially, I attempted to use the String.prototype.split() method with regex to separate the string, but encountered a problem due to files having underscores in their names. This led me to rethink my approach as the original solution was not effective.

The function I developed is as follows:

const shortenString = (attachmentName) => {
    const file = attachmentName
        .slice(attachmentName.indexOf('_') + 1)
        .slice(attachmentName.slice(attachmentName.indexOf('_') + 1).indexOf('_') + 1);

    const fileName = file.slice(0, file.lastIndexOf('.'));
    const fileType = file.slice(file.lastIndexOf('.'));

    return [fileName, fileType];
};

I am now exploring more elegant solutions to extract file names and types without resorting to loops.

javascript string algorithm

Answer 1

Answer №1

To extract the name and type from a string, you can utilize the functions replace and split. First, we replace everything up to the second underscore (_) from the beginning of the string. Then, we split the resulting string on the period (.) to separate the name and type.

https://i.sstatic.net/YhWul.png

let nameAndType = (str) => {
  let replaced =  str.replace(/^(?:[^_]*_){2}/g, '')
  let splited = replaced.split('.')
  let type = splited.pop()
  let name = splited.join('.')
  return {name,type}
}

console.log(nameAndType("1568223848_12345678_some_document.pdf"))
console.log(nameAndType("1568223848_12345678_some_document.xyz.pdf"))

Answer 2

To extract the name and type from a string, you can utilize the functions replace and split. First, we replace everything up to the second underscore (_) from the beginning of the string. Then, we split the resulting string on the period (.) to separate the name and type.

https://i.sstatic.net/YhWul.png

let nameAndType = (str) => {
  let replaced =  str.replace(/^(?:[^_]*_){2}/g, '')
  let splited = replaced.split('.')
  let type = splited.pop()
  let name = splited.join('.')
  return {name,type}
}

console.log(nameAndType("1568223848_12345678_some_document.pdf"))
console.log(nameAndType("1568223848_12345678_some_document.xyz.pdf"))

Answer 3

Answer №2

def removeUnderscore(val):
  return val.replace('_', ' ').strip()
}

Answer 4

def removeUnderscore(val):
  return val.replace('_', ' ').strip()
}

Answer 5

Answer №3


function extractFileName(input) {
    return input.replace(/^(?:[^_]*_){2}/g, '');
}

If the input is

1568223848_12345678_some_document.pdf

, the function should output some_document.pdf

Answer 6


function extractFileName(input) {
    return input.replace(/^(?:[^_]*_){2}/g, '');
}

If the input is

1568223848_12345678_some_document.pdf

, the function should output some_document.pdf

Answer 7

Answer №4

const pattern = /(.*?)_(.*?)_(.*)/;

const input = "1568223848_12345678_some_document.pdf";

[,date, id, filename] = pattern.exec(input);

console.log(date);
console.log(id);
console.log(filename);

Here are some key points to consider:

It is more efficient to define the regular expression once and reuse it.
```
function extractData(str) {
  const pattern = /expression/;
  ...
}
```
Creating a new regular expression object every time the function is called can impact performance.
Using non-greedy quantifiers like .*? can improve efficiency.

The non-greedy approach captures matches more efficiently by adding characters incrementally rather than greedily consuming the entire string at once.
While splitting on '_' may work, it could lead to excessive temporary strings.

For instance, if the filename is
```
1234_1343_a________________________.pdf
```
, there might be trade-offs between using regex or splitting for better speed optimization.

Answer 8

const pattern = /(.*?)_(.*?)_(.*)/;

const input = "1568223848_12345678_some_document.pdf";

[,date, id, filename] = pattern.exec(input);

console.log(date);
console.log(id);
console.log(filename);

Here are some key points to consider:

It is more efficient to define the regular expression once and reuse it.
```
function extractData(str) {
  const pattern = /expression/;
  ...
}
```
Creating a new regular expression object every time the function is called can impact performance.
Using non-greedy quantifiers like .*? can improve efficiency.

The non-greedy approach captures matches more efficiently by adding characters incrementally rather than greedily consuming the entire string at once.
While splitting on '_' may work, it could lead to excessive temporary strings.

For instance, if the filename is
```
1234_1343_a________________________.pdf
```
, there might be trade-offs between using regex or splitting for better speed optimization.

Answer 9

Answer №5

To obtain the second offset and beyond, you can use `.indexOf` in a chain, although it may become cumbersome with more than two occurrences. The rationale behind this is that the `indexOf` function accepts the starting index as its second parameter, allowing you to locate subsequent instances by referencing the index of the first one:

var secondUnderscoreIndex = name.indexOf("_",name.indexOf("_")+1);

Therefore, my proposed solution would be:

var index =  name.indexOf("_",name.indexOf("_")+1));
var [timestamp, name] = [name.substring(0, index), name.substr(index+1)];

Alternatively, one could utilize regular expressions:

var [,number1, number2, filename, extension] = /([0-9]+)_([0-9]+)_(.*?)\.([0-9a-z]+)/i.exec(name)
// Outputs: "1568223848 12345678 some_document pdf"
console.log(number1, number2, filename, extension);

Answer 10

To obtain the second offset and beyond, you can use `.indexOf` in a chain, although it may become cumbersome with more than two occurrences. The rationale behind this is that the `indexOf` function accepts the starting index as its second parameter, allowing you to locate subsequent instances by referencing the index of the first one:

var secondUnderscoreIndex = name.indexOf("_",name.indexOf("_")+1);

Therefore, my proposed solution would be:

var index =  name.indexOf("_",name.indexOf("_")+1));
var [timestamp, name] = [name.substring(0, index), name.substr(index+1)];

Alternatively, one could utilize regular expressions:

var [,number1, number2, filename, extension] = /([0-9]+)_([0-9]+)_(.*?)\.([0-9a-z]+)/i.exec(name)
// Outputs: "1568223848 12345678 some_document pdf"
console.log(number1, number2, filename, extension);

Answer 11

Answer №6

I appreciate simplicity...

If you ever require dates in a times format, they can be found in [1] and [2]

    let extractFileName = function(str) {
      return str.match(/(\d+)_(\d+)_(.*)/)[3];
    }

    let fileName = extractFileName("1568223848_12345678_some_document.pdf");
    console.log(fileName)

Answer 12

I appreciate simplicity...

If you ever require dates in a times format, they can be found in [1] and [2]

    let extractFileName = function(str) {
      return str.match(/(\d+)_(\d+)_(.*)/)[3];
    }

    let fileName = extractFileName("1568223848_12345678_some_document.pdf");
    console.log(fileName)

Answer 13

Answer №7

When dealing with file names in the format timestamp_id_filename, you can utilize a regular expression to exclude the first two '_' characters and extract the next one.

For example:

var filename = '1568223848_12345678_some_document.pdf';
console.log(filename.match(/[^_]+_[^_]+_(.*)/)[1]); // Output: 'some_document.pdf'

Explanation: /[^]+[^]+(.*)/

[^]+ : Match any character that is not '' : Match '' character This sequence skips over two '_' symbols before capturing the remaining characters (.*): Stores the matched characters in a group

The match method returns an array where the first element is the complete matched expression, while subsequent elements represent the saved groups.

Answer 14

When dealing with file names in the format timestamp_id_filename, you can utilize a regular expression to exclude the first two '_' characters and extract the next one.

For example:

var filename = '1568223848_12345678_some_document.pdf';
console.log(filename.match(/[^_]+_[^_]+_(.*)/)[1]); // Output: 'some_document.pdf'

Explanation: /[^]+[^]+(.*)/

[^]+ : Match any character that is not '' : Match '' character This sequence skips over two '_' symbols before capturing the remaining characters (.*): Stores the matched characters in a group

The match method returns an array where the first element is the complete matched expression, while subsequent elements represent the saved groups.

Answer 15

Answer №8

Separate the file name string by underscores and convert it into an array. Remove the first two items from the array. Combine the remaining elements with underscores. Voila, your file name is ready to go.

Answer 16

Separate the file name string by underscores and convert it into an array. Remove the first two items from the array. Combine the remaining elements with underscores. Voila, your file name is ready to go.

Is there a way to trim the string after the second occurrence of an underscore?

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

Answer №6

Answer №7

Answer №8

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