Split string at nth occurance of delimiter into array in javascript

Question

Is there a javascript/jquery method or function that will let me split a string at nth occurrence of a selected delimiter? I'd like it work just like the regular str.split(delimiter) except instead of splitting at every occurrence of the delimiter it could be instructed to skip n number of them each time.

var str = "A,BB,C,DDD,EEEE,F";
var strAry = str.split(",");

Would result in strAry looking like {"A","BB","C","DDD","EEEE","F"}

What I want would be {"A,BB","C,DDD","EEEE,F"} assuming I set nth occurance to 2.

I wrote a small function that appears to work but hoping there was a simpler way to do this:

function splitn(fullString, delimiter, n){
    var fullArray = fullString.split(delimiter);
    var newArray = [];
    var elementStr = "";
    for(var i = 0; i < fullArray.length; i++) {
        if (i == fullArray.length-1) {
            if (elementStr.length == 0) {
                elementStr = fullArray[i];
            } else {
                elementStr += (delimiter + fullArray[i]);
            }
            newArray.push(elementStr);
        } else {
            if (((i + 1) % n) == 0) {
                if (elementStr.length == 0) {
                    elementStr = fullArray[i];
                } else {
                    elementStr += (delimiter + fullArray[i]);
                }
                newArray.push(elementStr);
                elementStr = "";
            } else {
                if (elementStr.length == 0) {
                    elementStr = fullArray[i];
                } else {
                    elementStr += (delimiter + fullArray[i]);
                }
            }
        }
    };
    return newArray;
};

Thanks.

you could use regular split and then join back the pairs

Hogan
– Hogan

2015-09-12 01:23:40 +00:00
Commented Sep 12, 2015 at 1:23 — Hogan
– Hogan, Commented Sep 12, 2015 at 1:23

Etheryte · Accepted Answer · 2015-09-12 01:45:44Z

2

You could simply use Array.prototype.reduce() to modify the array returned by split to your liking. The idea is similar to your code, just shorter.

function modify(str, n, delim) {
    return str.split(delim).reduce(function(output, item, i) {
        if (!(i % n)) {
            output.push(item);
        } else {
            output[i / n | 0] += delim + item;
        };
        return output;
    }, []);
};

modify("A,BB,C,DDD,EEEE,F", 3, ','); //["A,BB,C", "DDD,EEEE,F"]
modify("A,BB,C,DDD,EEEE,F", 2, ','); //["A,BB", "C,DDD", "EEEE,F"]

edited Sep 12, 2015 at 1:45

answered Sep 12, 2015 at 1:37

Etheryte

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1 Comment

Alec Menconi Over a year ago

Oh nice, the reduce method is a new one to me. Thanks.

3 revs user1106925 · Accepted Answer · 2015-09-12 02:21:00Z

EDIT: Just noticed you wanted to use an arbitrary "nth" value. I updated it so you can simply change the nth to whatever positive integer you like.

Here's a way that takes advantage of the second argument to .indexOf() so that you can anchor your searches from after the last ending point in the string:

function splitn(fullString, delimiter, n) {
    var lastIdx = 0
    ,   idx = -1
    ,   nth = 0
    ,   result = [];

    while ((idx = fullString.indexOf(delimiter, idx + delimiter.length)) !== -1) {
      if ((nth = ++nth % n) === 0) {
        result.push(fullString.slice(lastIdx, idx));
        lastIdx = idx + 1;
      }
    }
    result.push(fullString.slice(lastIdx));
    return result;
}

var result = splitn("A,BB,C,DDD,EEEE,F", ",", 2);


document.body.innerHTML = "<pre>" + JSON.stringify(result, null, 4) + "</pre>";

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