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Acest capitol introduce modul de lucru cu string-uri și text, în JavaScript.


Tipul String al limbajului JavaScript este folosit pentru a representa date cu conținut text. Este un set de "elemente" cu valori întregi pe 16 biți, fără semn (unități de codificare UTF-16). Fiecare element din String ocupă o poziție în String. Primul element se află la poziția 0, următorul la poziția 1, și așa mai departe. Lungimea unui String este dată de numărul de elemente din String. Puteți crea string-uri folosind string-uri literali sau string-uri obiecte.

ATENȚIE: dacă editați această pagină nu includeți caractere peste U+FFFF, până ce bug-ul MDN 857438 este fixat ( ).

String-uri literali

Puteți crea string-uri simple folosind atât ghilimele simple cât și ghilimele duble:


String-uri mai avansate pot fi create folosind secvențe escape:

Secvențe escape hexazecimale

Numărul de după \x este interpretat ca fiind un număr hexazecimal.

'\xA9' // "©"

Secvențe escape Unicode

Secvențele escape Unicode au nevoie de cel puțin patru hexazecimale care să urmeze după \u.

'\u00A9' // "©"

Unicode code point escapes

New in ECMAScript 2015. With Unicode code point escapes, any character can be escaped using hexadecimal numbers so that it is possible to use Unicode code points up to 0x10FFFF. With simple Unicode escapes it is often necessary to write the surrogate halves separately to achieve the same.

See also String.fromCodePoint() or String.prototype.codePointAt().


// the same with simple Unicode escapes

String objects

The String object is a wrapper around the string primitive data type.

var s = new String('foo'); // Creates a String object
console.log(s); // Displays: {'0': 'f', '1': 'o', '2': 'o'}
typeof s; // Returns 'object'

You can call any of the methods of the String object on a string literal value—JavaScript automatically converts the string literal to a temporary String object, calls the method, then discards the temporary String object. You can also use the String.length property with a string literal.

You should use string literals unless you specifically need to use a String object, because String objects can have counterintuitive behavior. For example:

var s1 = '2 + 2'; // Creates a string literal value
var s2 = new String('2 + 2'); // Creates a String object
eval(s1); // Returns the number 4
eval(s2); // Returns the string "2 + 2"

A String object has one property, length, that indicates the number of UTF-16 code units in the string. For example, the following code assigns x the value 13, because "Hello, World!" has 13 characters, each represented by one UTF-16 code unit. You can access each code unit using an array bracket style. You can't change characters since strings are immutable array-like objects:

var mystring = 'Hello, World!';
var x = mystring.length;
mystring[0] = 'L'; // This has no effect
mystring[0]; // This returns "H"

Characters whose Unicode scalar values are greater than U+FFFF (such as some rare Chinese/Japanese/Korean/Vietnamese characters and some emoji) are stored in UTF-16 with two surrogate code units each. For example, a string containing the single character U+1F600 "Emoji grinning face" will have length 2. Accessing the individual code units in such a string using brackets may have undesirable consequences such as the formation of strings with unmatched surrogate code units, in violation of the Unicode standard. (Examples should be added to this page after MDN bug 857438 is fixed.) See also String.fromCodePoint() or String.prototype.codePointAt().

A String object has a variety of methods: for example those that return a variation on the string itself, such as substring and toUpperCase.

The following table summarizes the methods of String objects.

Methods of String

Method Description
charAtcharCodeAt, codePointAt Return the character or character code at the specified position in string.
indexOf, lastIndexOf Return the position of specified substring in the string or last position of specified substring, respectively.
startsWith, endsWith, includes Returns whether or not the string starts, ends or contains a specified string.
concat Combines the text of two strings and returns a new string.
fromCharCode, fromCodePoint Constructs a string from the specified sequence of Unicode values. This is a method of the String class, not a String instance.
split Splits a String object into an array of strings by separating the string into substrings.
slice Extracts a section of a string and returns a new string.
substring, substr Return the specified subset of the string, either by specifying the start and end indexes or the start index and a length.
match, replace, search Work with regular expressions.
toLowerCase, toUpperCase

Return the string in all lowercase or all uppercase, respectively.

normalize Returns the Unicode Normalization Form of the calling string value.
repeat Returns a string consisting of the elements of the object repeated the given times.
trim Trims whitespace from the beginning and end of the string.

Multi-line template literals

Template literals are string literals allowing embedded expressions. You can use multi-line strings and string interpolation features with them.

Template literals are enclosed by the back-tick (` `) (grave accent) character instead of double or single quotes. Template literals can contain place holders. These are indicated by the Dollar sign and curly braces (${expression}).


Any new line characters inserted in the source are part of the template literal. Using normal strings, you would have to use the following syntax in order to get multi-line strings:

console.log('string text line 1\n\
string text line 2');
// "string text line 1
// string text line 2"

To get the same effect with multi-line strings, you can now write:

console.log(`string text line 1
string text line 2`);
// "string text line 1
// string text line 2"

Embedded expressions

In order to embed expressions within normal strings, you would use the following syntax:

var a = 5;
var b = 10;
console.log('Fifteen is ' + (a + b) + ' and\nnot ' + (2 * a + b) + '.');
// "Fifteen is 15 and
// not 20."

Now, with template literals, you are able to make use of the syntactic sugar making substitutions like this more readable:

var a = 5;
var b = 10;
console.log(`Fifteen is ${a + b} and\nnot ${2 * a + b}.`);
// "Fifteen is 15 and
// not 20."

For more information, read about Template literals in the JavaScript reference.


The Intl object is the namespace for the ECMAScript Internationalization API, which provides language sensitive string comparison, number formatting, and date and time formatting. The constructors for Collator, NumberFormat, and DateTimeFormat objects are properties of the Intl object.

Date and time formatting

The DateTimeFormat object is useful for formatting date and time. The following formats a date for English as used in the United States. (The result is different in another time zone.)

var msPerDay = 24 * 60 * 60 * 1000;
// July 17, 2014 00:00:00 UTC.
var july172014 = new Date(msPerDay * (44 * 365 + 11 + 197));

var options = { year: '2-digit', month: '2-digit', day: '2-digit',
                hour: '2-digit', minute: '2-digit', timeZoneName: 'short' };
var americanDateTime = new Intl.DateTimeFormat('en-US', options).format;
console.log(americanDateTime(july172014)); // 07/16/14, 5:00 PM PDT

Number formatting

The NumberFormat object is useful for formatting numbers, for example currencies.

var gasPrice = new Intl.NumberFormat('en-US',
                        { style: 'currency', currency: 'USD',
                          minimumFractionDigits: 3 });
console.log(gasPrice.format(5.259)); // $5.259

var hanDecimalRMBInChina = new Intl.NumberFormat('zh-CN-u-nu-hanidec',
                        { style: 'currency', currency: 'CNY' });
console.log(hanDecimalRMBInChina.format(1314.25)); // ¥ 一,三一四.二五


The Collator object is useful for comparing and sorting strings.

For example, there are actually two different sort orders in German, phonebook and dictionary. Phonebook sort emphasizes sound, and it’s as if “ä”, “ö”, and so on were expanded to “ae”, “oe”, and so on prior to sorting.

var names = ['Hochberg', 'Hönigswald', 'Holzman'];
var germanPhonebook = new Intl.Collator('de-DE-u-co-phonebk');
// as if sorting ["Hochberg", "Hoenigswald", "Holzman"]:
console.log(names.sort(', '));
// logs "Hochberg, Hönigswald, Holzman"

Some German words conjugate with extra umlauts, so in dictionaries it’s sensible to order ignoring umlauts (except when ordering words differing only by umlauts: schon before schön).

var germanDictionary = new Intl.Collator('de-DE-u-co-dict');
// as if sorting ["Hochberg", "Honigswald", "Holzman"]:
console.log(names.sort(', '));
// logs "Hochberg, Holzman, Hönigswald"

For more information about the Intl API, see also Introducing the JavaScript Internationalization API.

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