JS / TS splitting string by a delimiter without removing the delimiter

user_1895488 0
Viewed 726

I have a string that I need to split by a certain delimiter and convert into an array, but without removing the delimiter itself. For example, consider the following code:

var str = "#mavic#phantom#spark";
str.split("#") //["", "mavic", "phantom", "spark"]

I need the output to be as follows:

["#mavic", "#phantom", "#spark"]

I read here but that does not answer my question.

typescript javascript
4 Answers

You could split by positive lookahead of #.

var string = "#mavic#phantom#spark",
    splitted = string.split(/(?=#)/);

console.log(splitted);

user_14476750

Split the string by # and use the reduce to return the modified string 

var str = "#mavic#phantom#spark";
let x = str.split("#").reduce((acc, curr) => {
  if (curr !== '') {
    acc.push('#' + curr);
  }
  return acc;
}, [])
console.log(x)

user_21813970

Here is also some non-regexp methods of solving your task:

Solution 1 classical approach - iterate over the string and each time when we find indexOf our delimiter, we push to the result array the substring between current position and the next position. In the else block we have a case for the last substring - we simply add it to the result array and break the loop.

const delimiter = '#';
const result1 = [];
let i = 0;
while (i < str.length) {
  const nextPosition = str.indexOf(delimiter, i+1);
  if (nextPosition > 0) {
    result1.push(str.substring(i, nextPosition));
    i = nextPosition;
  } else {
    result1.push(str.substring(i));
    break;
  }
}

Solution 2 - split the initial string starting at index 1 (in order to not include empty string in the result array) and then just map the result array by concatenating the delimiter and current array item.

const result2 = str.substr(1).split(delimiter).map(s => delimiter + s);
user_35510350

another way: filter empty elements after splitting, and map these elements to start with the character you splitted with.

string.split("#").filter((elem) => elem).map((elem) => "#" + elem);
user_29659040
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