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Файл:Технологии разработки клиентских WEB-приложений на языке JavaScript. Учебное пособие
.pdf
11
vr qw = 42; // qw Number
qw = "car"; // qw String
qw o = true; // qw Boolean
Выражения и операции
JavaSript,
JavScript
, x = 2 + 3),
2 + 3).
JavaSript
Unicode.
12
3
true
(==)
true,
3 == var1
"3" == var1
3 == '3'
(!=)
true,
var1 != 4
var2 != "3"
(===)
true,
Object.is sameness in JS
3 === var1
(!==)
true,
var1 !== "3"
3 !== '3'
(>)
true,
var2 > var1
"12" > 2
(>=)
true,
var2 >= var1
var1 >= 3
(<)
true,
var1 < var2
"2" < 12
(<=)
true,
var1 <= var2
var2 <= 5
13
4
+
6 + 9
-
20 - 15
*
3 * 7
/
10 / 5
%
11 % 3 =
2 3
2)
**
ES
2016.
5 ** 5
3125,
5*5*5*5*5)
JavaSript
-
32
Number.
14
5
a & b
1
1.
a | b
1
1.
a ^ b
1
1.
~ a
a << b
a
b
a >> b
a
b
a >>> b
a
b
(&&)
expr1 && expr2
expr1,
false;
expr2.
Boolean
&& true,
true;
&& false.
6
15
6
(||)
expr1 || expr2
expr1,
true;
expr2.
Boolean
|| true
true; false.
(!)
!expr
false
expr true;
true.
x = y
x = y
x += y
x = x + y
x -= y
x = x - y
x *= y
x = x * y
x /= y
x = x / y
x %= y
x = x % y
x <<= y
x = x << y
x >>= y
x = x >> y
x >>>= y
x = x >>> y
AND
x &= y
x = x & y
XOR
x ^= y
x = x ^ y
OR
x |= y
x = x | y
a = b, a
b.
7
16
let theNumber = Number(prompt("Pick a number"));
if (!Number.isNaN(theNumber)) {
console.log("Your number is the square root of " +
theNumber * theNumber);
}
if (1 + 1 == 2) console.log("It's true");
// It's true
delete, new
Управляющие конструкции языка JavaSсript
Условный оператор IF
if JavaScript.
-
parrot,
if
Number.isNaN JavaScript,
true NaN. Number NaN,
theNumber
if
JavaScript
17
let num = Number(prompt("Pick a number"));
if (num < 10) {
console.log("Small");
} else if (num < 100) {
console.log("Medium");
} else {
console.log("Large");
}
console.log(0);
console.log(2);
console.log(4);
console.log(6);
console.log(8);
console.log(10);
console.log(12);
else if
if / else
num, 10.
Small
else, if.
(<100) 10
100,
Оператор цикла DO/WHILE
0 12.
-
1000,
18
let number = 0;
while (number <= 12) {
console.log(number);
number = number + 2;
}
// 0
// 2
// etcetera
let result = 1;
let counter = 0;
while (counter < 10) {
result = result * 2;
counter = counter + 1;
}
console.log(result);
// 1024
-
while,
while
if.
true
2
12,
-
210 2 10-
2. 10,
1 <= 10,
4,
0.
do - while.
do
19
let yourName;
do {
yourName = prompt("Who are you?");
} while (!yourName);
console.log(yourName);
for (let number = 0; number <= 12; number = number + 2) {
console.log(number);
}
// 0
// 2
// etcetera
-
"", true.
Оператор цикла FOR
while,
JavaScript
for.
for.
for
-
while.
210,
20
let result = 1;
for (let counter = 0; counter < 10; counter = counter + 1) {
result = result * 2;
}
console.log(result);
// 1024
for ... in
for (variablename in object) {
statement or block to execute
}
for (let current = 20; ; current = current + 1) {
if (current % 7 == 0) {
console.log(current);
break;
}
}
// 21
JavaScript,
Оператор прерывания BREAK
false -
break,
break.
20 7.
remainder (%) -
for
break
break
true,
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