mozilla
Wyniki wyszukiwania

    String

    To tłumaczenie jest niekompletne. Pomóż przetłumaczyć ten artykuł /a> z języka angielskiego.

    Podsumowanie

    Tworzy obiekt pozwalający działać na ciągach znaków.

    Składnia

    Literały znakowe są postaci:

    'string text'
    "string text"
    "中文 español English हिन्दी العربية português বাংলা русский 日本語 ਪੰਜਾਬੀ 한국어 தமிழ்"
    

    Beside regular, printable characters, special characters can be encoded using escape notation:

    Code Output
    \0 the NUL character
    \' single quote
    \" double quote
    \\ backslash
    \n new line
    \r carriage return
    \v vertical tab
    \t tab
    \b backspace
    \f form feed
    \uXXXX unicode codepoint
    \xXX the Latin-1 character

    Or, using the String global object directly:

    String(thing)
    new String(thing)
    

    Parametry

    thing
    Dowolny łańcuch znaków.

    Opis

    trings are useful for holding data that can be represented in text form. Some of the most-used operations on strings are to check their length, to build and concatenate them using the + and += string operators, checking for the existence or location of substrings with the indexOf() method, or extracting substrings with the substring() method.

    Character access

    There are two ways to access an individual character in a string. The first is the charAt() method:

    return 'cat'.charAt(1); // returns "a"
     

    The other way (introduced in ECMAScript 5) is to treat the string as an array-like object, where individual characters correspond to a numerical index:

    return 'cat'[1]; // returns "a"
     

    For character access using bracket notation, attempting to delete or assign a value to these properties will not succeed. The properties involved are neither writable nor configurable. (See Object.defineProperty() for more information.)

    Comparing strings

    C developers have the strcmp() function for comparing strings. In JavaScript, you just use the less-than and greater-than operators:

    var a = 'a';
    var b = 'b';
    if (a < b) { // true
      print(a + ' is less than ' + b);
    } else if (a > b) {
      print(a + ' is greater than ' + b);
    } else {
      print(a + ' and ' + b + ' are equal.');
    }

    A similar result can be achieved using the localeCompare() method inherited by String instances.

    Distinction between string primitives and String objects

    Note that JavaScript distinguishes between String objects and primitive string values. (The same is true of Boolean and Numbers.)

    String literals (denoted by double or single quotes) and strings returned from String calls in a non-constructor context (i.e., without using the new keyword) are primitive strings. JavaScript automatically converts primitives to String objects, so that it's possible to use String object methods for primitive strings. In contexts where a method is to be invoked on a primitive string or a property lookup occurs, JavaScript will automatically wrap the string primitive and call the method or perform the property lookup.

    var s_prim = 'foo';
    var s_obj = new String(s_prim);
    
    console.log(typeof s_prim); // Logs "string"
    console.log(typeof s_obj);  // Logs "object"
     

    String primitives and String objects also give different results when using eval(). Primitives passed to eval are treated as source code; String objects are treated as all other objects are, by returning the object. For example:

    var s1 = '2 + 2';             // creates a string primitive
    var s2 = new String('2 + 2'); // creates a String object
    console.log(eval(s1));        // returns the number 4
    console.log(eval(s2));        // returns the string "2 + 2"

    For these reasons, code may break when it encounters String objects when it expects a primitive string instead, although generally authors need not worry about the distinction.

    A String object can always be converted to its primitive counterpart with the valueOf() method.

    console.log(eval(s2.valueOf())); // returns the number 4
    Note: For another possible approach to strings in JavaScript, please read the article about StringView — a C-like representation of strings based on typed arrays.

    Własności

    For własności available on String instances, see Własności of String instances.
    String.prototype
    Pozwala na dodawanie własności do obiektu String.
    Properties inherited from Function:

    Metody

    For methods available on String instances, see Methods of String instances.
    String.fromCharCode()
    Zwraca łańcuch znaków stworzony przez podaną sekwencję kodów Unicode.
    String.fromCodePoint()
    Returns a string created by using the specified sequence of code points.
    String.raw()
    Returns a string created from a raw template string.
    Methods inherited from Function:

    Przykłady

    Example: String conversion

    It's possible to use String as a "safer" toString() alternative, as although it still normally calls the underlying toString(), it also works for null and undefined. For example:

    var outputStrings = [];
    for (var i = 0, n = inputValues.length; i < n; ++i) {
      outputStrings.push(String(inputValues[i]));
    }
     

    Autorzy i etykiety dokumentu

    Etykiety: 
    Contributors to this page: JasonSpiro, grzegorz, teoli, VooEak, Internauta1024A, Mgjbot, Ptak82
    Ostatnia aktualizacja: teoli,
    Ukryj panel boczny