# Category Programming

### JS Code Editor (Try)

https://www.w3schools.com/js/tryit.asp?filename=tryjs_output_dom

## The if Statement

Use the if statement to specify a block of JavaScript code to be executed if a condition is true.

Syntax

if (condition) {

block of code to be executed if the condition is true

}

Note that if is in lowercase letters. Uppercase letters (If or IF) will generate a JavaScript error.

Example

Make a «Good day» greeting if the hour is less than 18:00:

if (hour < 18) {

greeting = «Good day»;

}

The result of greeting will be:

Good day

## JavaScript Arithmetic Operators

Arithmetic operators are used to perform arithmetic on numbers:

Operator Description

— Subtraction

* Multiplication

/ Division

% Modulus

++ Increment

— Decrement

## JavaScript Assignment Operators

Assignment operators assign values to JavaScript variables.

Operator Example Same As

= 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

Example

var x = 10;

x += 5;

## JavaScript String Operators

The + operator can also be used to add (concatenate) strings.

Example

txt1 = «John»;

txt2 = «Doe»;

txt3 = txt1 + » » + txt2;

The result of txt3 will be:

John Doe

The += assignment operator can also be used to add (concatenate) strings:

Adding two numbers, will return the sum, but adding a number and a string will return a string:

Example

x = 5 + 5;

y = «5» + 5;

z = «Hello» + 5;

The result of x, y, and z will be:

10

55

Hello5

## JavaScript Comparison Operators

Operator Description

== equal to

=== equal value and equal type

!= not equal

!== not equal value or not equal type

> greater than

< less than

>= greater than or equal to

<= less than or equal to

? ternary operator

## JavaScript Logical Operators

Operator Description

&& logical and

|| logical or

! logical not

## JavaScript Type Operators

Operator Description

typeof Returns the type of a variable

instanceof Returns true if an object is an instance of an object type

Type operators are fully described in the JS Type Conversion chapter.

## JavaScript Bitwise Operators

Bit operators work on 32 bits numbers.

Any numeric operand in the operation is converted into a 32 bit number. The result is converted back to a JavaScript number.

Operator Description Example Same as Result Decimal

& AND 5 & 1 0101 & 0001 0001 1

| OR 5 | 1 0101 | 0001 0101 5

~ NOT ~ 5 ~0101 1010 10

^ XOR 5 ^ 1 0101 ^ 0001 0100 4

<< Zero fill left shift 5 << 1 0101 << 1 1010 10

>> Signed right shift 5 >> 1 0101 >> 1 0010 2

>>> Zero fill right shift 5 >>> 1 0101 >>> 1 0010 2

The examples above uses 4 bits unsigned examples. But JavaScript uses 32-bit signed numbers.

Because of this, in JavaScript, ~ 5 will not return 10. It will return -6.

~00000000000000000000000000000101 will return 11111111111111111111111111111010

Bitwise operators are fully described in the JS Bitwise chapter.

&&

||

==

===

!boolevo

### LINUX Debian 8

RUN .SH
bash /test.sh

Разрешить исполнение SH

chmod ugo+x sript.sh