How to take part of a String up to a specified character?

Question

I would like a Javascript method that takes part of a String up to a certain point (character) from it. In this case I would specify a character and only be taken part of the String until the character I specified.

• I wouldn’t want to use the methods substring, indexOf or the split. Because they require me to do this in more than one line of code (using array or indexes) and, in my specific problem, it needs to be done in a single line.

Example of what I would need:

let frase = "99 troços";

//Eu precisaria disso (que está abaixo) só que sem utilizar outras linhas de código antes da variável armazenarValor.
let armazenarValor = "99"; //Ignoraria o espaço e o 'troços'.


//Eu precisaria que ficasse algo assim
let armazenarValor = pegarAteEspaco(frase, " ");
//Imaginemos que pegarAteEspaco() fosse um método JavaScript que pegasse uma String até determinado caracter.
//Eu só gostaria de pegar o "99" e ignorar o resto.

• I couldn’t do a function for that either.
• In PHP there are methods that do this. But I would like to do in JS.
• I saw some things here at the Stack Overflow, but most are using substring, split or indexOf.
• Maybe there isn’t something native to JS made exactly for this.

Answer 1

You can use a regular expression to do this:

const string = '99 troços';

const [, match] = string.match(/(\S+) /) || [];

console.log(match);

In the above regular expression, we create a capture group to get the desired value. Within this group, we use \S+ to give match in one or more characters other than white space (such as spaces, line breaks, tabs, etc.). Then we hope that always after this capture group, there is a space.

Like the String.prototype.match can return null if regular expression does not find occurrences, I used a fallback at the end, so that a array always be returned, and always be able to do the de-structuring.

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You can also write the code in a single line:

const [, match] = '99 troços'.match(/(\S+) /) || [];
console.log(match);

// Ou se você realmente quiser em uma linha mesmo:
console.log(('99 troços'.match(/(\S+) /) || [])[1]);

But I really don’t know why you would want to do that, since it makes the code quite unreadable, at least using this form. As placed in the comments (here, by @bfavaretto; and here, by @hkotsubo), there are other more "elegant" ways to do this in a single line.

Answer 2

Well, there is an alternative - in my opinion, kind of "ugly" - and that "serves" specifically for the case of the question (which has numbers at the beginning). I leave it here as a curiosity:

let frase = "99 troços";
let valor = parseInt(frase);
console.log(valor); // 99

That just "works" because according to the documentation of parseInt:

If parseInt Encounters a Character that is not a numeral in the specified Radix, it ignores it and all succeeding characters and Returns the integer value Parsed up to that point.

In free translation:

If parseInt finds a character that is not a numeral in the specified base, it ignores this and all of the following characters and returns the integer that was read up to that point.

I mean, he reads the 99 and when you find the space, stop reading. At the end the result is 99.

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Of course, if the situation is different (string does not start with numbers, etc.), then it is better to use the solutions of the other answers. Although for these cases I still prefer to use substring, split and indexOf.

Answer 3

I did not understand this requirement not to use the method String.prototype.split() is a native method of language splits a String object into an array of strings by separating the string into substrings.

In this case instead of searching for separations just limit the action of the method to the first occurrence of the separator through the parameter limite.

let texto = "99 troços a 99 centavos ";

console.log(pegarAteEspaco(texto, " "));

function pegarAteEspaco(frase, separador) {
  return frase.split(separador, 1)[0]
}

Same code on one line:

console.log("99 troços a 99 centavos ".split(" ", 1)[0])