JavaScript . , .

UTF-16, .

JavaScript .

, :

let single = 'single-quoted';
let double = "double-quoted";

let backticks = `backticks`;

, , , , , ${}:

function sum(a, b) {
  return a + b;
}

alert(`1 + 2 = ${sum(1, 2)}.`); // 1 + 2 = 3.

, :

let guestList = `Guests:
 * John
 * Pete
 * Mary
`;

alert(guestList); //  ,    

, ? ? , :

let guestList = "Guests: // Error: Unexpected token ILLEGAL
  * John";

: . , , .

. : func`string`. func . . , . , .

, , \n:

let guestList = "Guests:\n * John\n * Pete\n * Mary";

alert(guestList); //  ,    

, , -:

//        
let str1 = "Hello\nWorld";

//  ,     
let str2 = `Hello
World`;

alert(str1 == str2); // true

, . :

, , \ .

, .

:

alert( 'I\'m the Walrus!' ); // I'm the Walrus!

\' .

, , , . , :

alert( `I'm the Walrus!` ); // I'm the Walrus!

, \ , . , \. alert .

, \?

, !

alert( `The backslash: \\` ); // The backslash: \

length :

alert( `My\n`.length ); // 3

, \n , : 3.

, pos, : [pos]. str.at(pos). :

let str = `Hello`;

//   
alert( str[0] ); // H
alert( str.at(0) ); // H

//   
alert( str[str.length - 1] ); // o
alert( str.at(-1) ); // o

, .at(pos) , . pos , .

, .at(-1) , .at(-2) , , ..

undefined . :

let str = `Hello`;

alert( str[-2] ); // undefined
alert( str.at(-2) ); // l

, for..of:

for (let char of "Hello") {
  alert(char); // H,e,l,l,o (char   "H",  "e",  "l"  ..)
}

JavaScript . . .

, , :

let str = 'Hi';

str[0] = 'h'; // 
alert( str[0] ); //  

.

:

let str = 'Hi';

str = 'h' + str[1]; //  

alert( str ); // hi

.

toLowerCase() toUpperCase() :

alert( 'Interface'.toUpperCase() ); // INTERFACE
alert( 'Interface'.toLowerCase() ); // interface

- :

alert( 'Interface'[0].toLowerCase() ); // 'i'

.

str.indexOf

str.indexOf(substr, pos).

substr str, pos, , , -1 .

:

let str = 'Widget with id';

alert( str.indexOf('Widget') ); // 0,    'Widget'   
alert( str.indexOf('widget') ); // -1,  ,    

alert( str.indexOf("id") ); // 1,  "id"    1 (..idget with id)

.

, "id" 1. , , 2:

let str = 'Widget with id';

alert( str.indexOf('id', 2) ) // 12

, indexOf . , , :

let str = ' -   ';

let target = ''; //  

let pos = 0;
while (true) {
  let foundPos = str.indexOf(target, pos);
  if (foundPos == -1) break;

  alert( ` : ${foundPos}` );
  pos = foundPos + 1; //    
}

:

let str = " -   ";
let target = "";

let pos = -1;
while ((pos = str.indexOf(target, pos + 1)) != -1) {
  alert( pos );
}

indexOf if . :

let str = "Widget with id";

if (str.indexOf("Widget")) {
    alert(" "); //  
}

"Widget", , 0. alert , . . str.indexOf("Widget") 0, if , .

-1:

let str = "Widget with id";

if (str.indexOf("Widget") != -1) {
    alert(" "); //  
}

~. 32- (signed 32-bit integer). , , , . .

: 32- ~n -(n+1).

:

alert( ~2 ); // -3,  ,  -(2+1)
alert( ~1 ); // -2,  ,  -(1+1)
alert( ~0 ); // -1,  ,  -(0+1)
alert( ~-1 ); // 0,  ,  -(-1+1)

, ~n 0 n == -1 ( n, 32- ).

, if ( ~str.indexOf("") ) , indexOf -1, .

, indexOf :

let str = "Widget";

if (~str.indexOf("Widget")) {
  alert( ' ' ); // 
}

- , , .

: if (~str.indexOf()) .

, , - , 32 ~, , 0, ~4294967295=0. .

, : .includes (. ).

includes, startsWith, endsWith

str.includes(substr, pos) true, str substr, false, .

, , , :

alert( "Widget with id".includes("Widget") ); // true

alert( "Hello".includes("Bye") ); // false

str.includes :

alert( "Midget".includes("id") ); // true
alert( "Midget".includes("id", 3) ); // false,     3

str.startsWith str.endsWith , , :

alert( "Widget".startsWith("Wid") ); // true, "Wid"   "Widget"
alert( "Widget".endsWith("get") ); // true, "get"   "Widget"

JavaScript 3 : substring, substr slice.

str.slice(start [, end])

start ( ) end.

:

let str = "stringify";
// 'strin',   0  5 (  5)
alert( str.slice(0, 5) );
// 's',  0  1,   1, . .      0
alert( str.slice(0, 1) );

end , slice :

let str = "stringify";
alert( str.slice(2) ); // ringify,   2   

start/end . , :

let str = "stringify";

//    4 ,     1 
alert( str.slice(-4, -1) ); // gif

str.substring(start [, end])

start end ( ) end.

, slice, start end.
start end, substring , .

:

let str = "stringify";

//  substring     
alert( str.substring(2, 6) ); // "ring"
alert( str.substring(6, 2) ); // "ring"

//    slice:
alert( str.slice(2, 6) ); // "ring" (  )
alert( str.slice(6, 2) ); // "" ( )

substring, slice, , 0.

str.substr(start [, length])

start length.

, :

let str = "stringify";
// ring,  4 ,    2
alert( str.substr(2, 4) );

, :

let str = "stringify";
// gi,  2 ,    4   
alert( str.substr(-4, 2) );

Annex B . , JavaScript, . .

, , :

, .

, .

1. :

   alert( 'a' > 'Z' ); // true

2. , , :

   alert( 'sterreich' > 'Zealand' ); // true

   : , Zealand sterreich .

, , JavaScript.

UTF-16. , . , .

str.codePointAt(pos)

, pos:

//          
//    
alert( "z".codePointAt(0) ); // 122
alert( "Z".codePointAt(0) ); // 90

String.fromCodePoint(code)

code

alert( String.fromCodePoint(90) ); // Z

, 65 220 :

let str = '';

for (let i = 65; i <= 220; i++) {
  str += String.fromCodePoint(i);
}
alert( str );
// ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~
// 

, , , .

, a > Z.

. . a (97) Z (90).

• , .
• , , . , a z.

, , .

, .

, ( IE10 Intl.JS) ECMA 402, .

.

str.localeCompare(str2) , , :

• , str str2.
• , str str2.
• 0, .

:

alert( 'sterreich'.localeCompare('Zealand') ); // -1

, . ( ) . , , "a" "a".

• . , , ${}.
• JavaScript UTF-16.
• , \n.
• [] at.
• slice substring.
• , , toLowerCase/toUpperCase.
• indexOf includes/startsWith/endsWith, , .
• , localeCompare.

- :

• str.trim() .
• str.repeat(n) n .
• , .

. , .

, , , . , .