How do I create a function that extracts the middle to end of strings of different lengths?

user_19544951 0
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I am trying to make a function that adds a space between "flight" and "###" but would like to make it work if the flight number is greater than 3 digits. I know I could make the second part of the slice method a huge number and it would technically work but I figure there should be a more elegant way. Any help would be appreciated, thanks!

const addSpace = function (str) {
      const flightNumber = str.slice(6, 9);
      return [str.slice(0, 6) + ' ' + flightNumber]
    }
    
    console.log(...addSpace('flight843'));
spacing function javascript string
3 Answers

You can match 6 characters a-z and 3 or more digits using a pattern with 2 capture groups.

In the replacement use the 2 capture groups with a space in between.

const addSpace = str => str.replace(/\b([a-z]{6})(\d{3,})\b/g, "$1 $2");
console.log(addSpace('flight843'));

You can also literally match flight, and append anchors if that is the only allowed string.

^(flight)(\d{3,})$
user_54249880

As flight string will always be there. We can simply achieve this by using String.replace() method. I also done the performance test in jsbench and it runs fastest among all the solutions mentioned here.

Live Demo :

const addSpace = function (str) {
  const len = str.replace('flight', '').length;
  return len > 3 ? str.replace('flight', 'flight ') : str
}

console.log(addSpace('flight843')); // 'flight843'
console.log(addSpace('flight8432')); // 'flight 8432'

user_41163000

If you need only addSpace I belived this is a simple solution for your quest. With this dynamic function is possible add Space for many block of words.

/* ADD Spacing */

 const string = "flightNumber";
 const dataValue = "flight";

 function addSpacing(str, data){

    //Verify if exist the wolrd in the string

    if(str.includes(data)){

        //get the word
        let word = str.substr(0, data.length);

        //Add Capitalise
        let strCapitalize = word.charAt(0).toUpperCase();

        let cleanword = word.slice(1, +data.length);

        //add spacing
        let newStr = str.replace(word, strCapitalize + cleanword + " ");
        
        console.log(newStr);

    }

 }

 addSpacing(string, dataValue);
user_140864670
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