This is just an example, I have much more amount of data:

var str = "3.0;4.5;5.2;6.6";
var res = str.split(";");
console.log(res);

The output will be an array of strings. How can I have array of numbers without going through the existing array again?

This is just an example, I have much more amount of data:

var str = "3.0;4.5;5.2;6.6";
var res = str.split(";");
console.log(res);

The output will be an array of strings. How can I have array of numbers without going through the existing array again?

• javascript

Share Follow asked Dec 14, 2018 at 10:26 user3719454user3719454 1,01611 gold badge1212 silver badges2727 bronze badges 3

• This is an exsisting post: stackoverflow./questions/15677869/… – C4mps Commented Dec 14, 2018 at 10:31
• 4 This question is different from both of those questions, because of the "without going through the existing array again". – T.J. Crowder Commented Dec 14, 2018 at 10:41
• 3 In 99% of cases people add these restrictions because they mistakenly think that avoiding loops will somehow improve performance, when in fact convoluted solutions without loops are often much worse performancewise. – JJJ Commented Dec 14, 2018 at 12:16

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5 Answers 5

Sorted by: Reset to default 6

...without going through the existing array again?

That's tricky. You can't with split, because split produces an array of strings. You could do it in a single pass with a regular expression, building the array yourself:

var rex = /[^;]+/g;
var str = "3.0;4.5;5.2;6.6";
var match;
var res = [];
while ((match = rex.exec(str)) != null) {
  res.push(+match[0]);
}
console.log(res);

Or actually, that's more overhead than necessary, just indexOf and substring will do:

var str = "3.0;4.5;5.2;6.6";
var start = 0, end;
var res = [];
while ((end = str.indexOf(";", start)) !== -1) {
  res.push(+str.substring(start, end));
  start = end + 1;
}
if (start < str.length) {
  res.push(+str.substring(start));
}
console.log(res);

KooiInc's answer uses replace to do the loop for us, which is clever.

---

That said, unless you have a truly massive array, going through the array again is simpler:

var res = str.split(";").map(entry => +entry);

---

In the above, I convert from string to number using a unary +. That's only one of many ways, and they have pros and cons. I do a rundown of the options in this answer.

You can use map():

var str = "3.0;4.5;5.2;6.6";
var res = str.split(";").map(Number);
console.log(res);

You could replace all the ; using regex with , and then use JSON.parse() to convert it to an array of numbers:

var str = "3;4;5;6".replace(/;/g, ',');
var res = JSON.parse("["+str+"]");
console.log(res);

Do note though, in terms of its efficiency, this isn't any better than using a simple .map to go through the array again.

Another idea without split:

const str2Numbers = (str, numbers = []) => 
 str.replace(/[^;]+/g, a => numbers.push(+a)) && numbers;
console.log(str2Numbers("3.0;4.5;5.2;6.6;3421"));

That's tricky. You can't with split, because split produces an array of strings.

var str = "3.0;4.5;5.2;6.6";
var res = str.split(',').map(function(number) {
    console.log(res);
    return parseInt(number, 10);    
});