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Operator Precedence and associativity in JavaScript

Operator Precedence

Operator precedence determines the order in which operators are evaluated when more than one operator is used in an expression.

The higher an operator’s precedence, the earlier it is evaluated in comparison with the operators with lower precedence.

Consider the following example:

a+b*c

a+b*c

The above expression is evaluated in the order of the multiplication operator (*) at first, then the plus operator (+), and finally, the assignment operator (=), due to their respective precedence order.

Precedence can also be manually overridden using a parenthesis e.g.,

(a+b)*c

(a+b)*c

The above mentioned expression has its parenthesis around the plus operator, which alters the precedence thereby evaluating the addition operation first.

Operator Associativity

Associativity determines the way in which the operators having same precedence are parsed e.g.:

a <operator> b <operator> c

1	a <operator> b <operator> c

Left-associativity (left to right) denotes that it is processed as (a <operator> b) <operator> c, while right-associativity (right to left) denotes it is interpreted as a <operator> (b <operator>c).

Assignment operators are right-associative i.e.,

a = b = 5;

1	a = b = 5;

Here both a and b get the same value 5.

At first, b is set to 5.

Then a is also initialized to 5 i.e., the return value of b = 5(right operand of the assignment).

Operator Precedence Table

In the following table, the highest precedence refers to 20 and to the lowest to 1.

Precedence	Operator type	Associativity	Individual operators
20	Grouping	n/a	(…)
19	Member Access (dot operator)	left-to-right	… . …
	Computed Member Access	left-to-right	… [ … ]
	new (with argument list)	n/a	new … ( … )
	Function Call	left-to-right	… ( `…` )
18	new (without argument list)	right-to-left	new …
17	Postfix Increment	n/a	… ++
17	Postfix Decrement	n/a	… —
16	Logical NOT	right-to-left	! …
	Bitwise NOT		~ …
	Unary Plus		+ …
	Unary Negation		– …
	Prefix Increment		++ …
	Prefix Decrement		— …
	typeof		typeof …
	void		void …
	delete>		delete …
	await		await …
15	Exponentiation	right-to-left	… ** …
14	Multiplication	left-to-right	… * …
	Division		… / …
	Remainder		… % …
13	Addition	left-to-right	… + …
13	Subtraction	left-to-right	… – …
12	Bitwise Left Shift	left-to-right	… << …
	Bitwise Right Shift		… >> …
	Bitwise Unsigned Right Shift		… >>> …
11	Less Than	left-to-right	… < …
	Less Than Or Equal		… <= …
	Greater Than		… > …
	Greater Than Or Equal		… >= …
	in		… in …
	instanceof		… instanceof …
10	Equality	left-to-right	… == …
	Inequality		… != …
	Strict Equality		… === …
	Strict Inequality		… !== …
9	Bitwise AND	left-to-right	… & …
8	Bitwise XOR	left-to-right	… ^ …
7	Bitwise OR	left-to-right	… \| …
6	Logical AND	left-to-right	… && …
5	Logical OR	left-to-right	… \|\| …
4	Conditional	right-to-left	… ? … : …
3	Assignment	right-to-left	… = …
			… += …
			… -= …
			… **= …
			… *= …
			… /= …
			… %= …
			… <<= …
			… >>= …
			… >>>= …
			… &= …
			… ^= …
			… \|= …
2	yield	right-to-left	yield …
2	yield*	right-to-left	yield* …
1	Comma / Sequence	left-to-right	… , …

HTML del tag

HTML del tag is used to represent set of characters deleted from the document. The characters inside the del tag are represented as text with centre line(text with strukethrough line).

Syntax:

<del>.......</del>

1	<del>.......</del>

Example:

Result:

Java StringTokenizer hasMoreElements() Method

This method checks for next token in StringTokenizer if the token exists then return true else return false. Work similar as
hasMoreToken()

Parameters

Return

Return true if next token exists else return false

Example

package ebhor;

import java.util.StringTokenizer;

public class StringTokenizer5 {
    public static void main(String[] args) {
        StringTokenizer st=new StringTokenizer("Java is secure language");
        boolean b=st.hasMoreElements();
        System.out.println("Has More Element :"+b);
   }
 }

package ebhor;

import java.util.StringTokenizer;

public class StringTokenizer5 {

public static void main(String[] args) {

StringTokenizer st=new StringTokenizer("Java is secure language");

boolean b=st.hasMoreElements();

System.out.println("Has More Element :"+b);

}

Result

Has More Element :true

1	Has More Element :true

At starting object st is pointing before the first word(Java). on calling st.hasMoreElements it is checkin that the first word java is there so it is returning true.

MySql Update table column from another table colunm

Updating a table fields from another table columns we can user following syntax

Update table1 inner join table2
on a.id=b.id
set
 a.field1=b.field1
b.field2=b.field3

Update table1 inner join table2

on a.id=b.id

set

a.field1=b.field1

b.field2=b.field3

There are two tables table1 and table2. Both table have common id value. To select appropriate field from table inner join in used and updating table1 fields from table2 fields set statement is used.

For example there are two tables with following fields
user(id,fname,lname,mobileno,address,);
personal(id,fname,lname,mobile_no);

Here c=consider user and person have common id then to update user from person we can use following query

update user as u 
  inner join person p 
on
 u.id=p.id 
set u.fname=p.fname,
    u.lname=p.lname, 
    u.mobile_no=p.mobno;

update user as u

inner join person p

u.id=p.id

set u.fname=p.fname,

u.lname=p.lname,

u.mobile_no=p.mobno;

This will update user table with person tables fields.

Nginx and tomcat server configuration

server {
  listen          80;
  root            /opt/tomcat/webapps/ROOT/;//or path where you want to redirect the nginx serviceN
   server_name mysite.com www.mysite.com;
   server_name_in_redirect off;
    access_log /var/log/nginx/site/site_access.log;
    error_log /var/log/nginx/site/site_error.log debug;

  location / {
        proxy_set_header Host $host;
        proxy_set_header X-Forwarded-Server $host;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_cookie_path ~*^/.* /;
        proxy_pass http://localhost:8080;
  }
}

server {

listen 80;

root /opt/tomcat/webapps/ROOT/;//or path where you want to redirect the nginx serviceN

server_name mysite.com www.mysite.com;

server_name_in_redirect off;

access_log /var/log/nginx/site/site_access.log;

error_log /var/log/nginx/site/site_error.log debug;

location / {

proxy_set_header Host $host;

proxy_set_header X-Forwarded-Server $host;

proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;

proxy_cookie_path ~*^/.* /;

proxy_pass http://localhost:8080;

}

Algebraic expression

A combination of constant and variables connected by some or all at the the four fundamental operations, additions, substraction, multiplication & division is called an algabric expression
e.g- 3x + zy

Terms:- the different part of an algebraic expression separated by sign+ or – are called the terms of an expression.
e.g. 3x+2y (term – 3x & 2y)

factor of terms :- we can factroized all terms all terms.-
e.g 3x + 2y
3x = 3×x
2y = 2×y

Types of algebaric expressions.

Monomial– which contains only one term is said a monimial.
Ginomial– which contains two terms e.g. 3x + 2y
Trinomials– which contains three terms – e.g- 3x +2y +z
Quadrinomials – which contains four terms e.g. 2x + 3y + z-6
Polynomials– which contains one or more terms.

Degree of polynomials The highest power of the variable in a polynomials is called its degree.

$x^{3}+3, \frac{1}{2}, y^3+1$ Here the degree of the polynomial is 3

Linear polynomial– a polynomial of degree is called a linear polynomials. E.g.- x+3

Quadratic polynomials– a polynomials of degree 2 is called a quadratic polynomials.

E.g. (x+2)(x+3) = x2 + 5x + 6

Cubic polynomial– A polynomial of degree 3 is called cubic polynomials.
e.g. degree of the term- 3x =1
2xy = 1+1 = 2
3x2g = 2 = 1 = 3

Algebraic expressions contains one or more forms and each terms contain variable and numerical coefficient, we find the value of terms to put the value of variables.
Equation– a statement of equality which invader one or more variable is called an equation. Terms of left hand side is equal to right hand side e.g – 3x+5 = 8

Solution of an equation e.g. 3x+5=8

(1 )Trial & error method– put the value of variable x, so that L.H.S= R.H.S.
Put the value of x= 1,2,3 who satisfy by the equation
3(1)=5 =8 the value of x= 1 is satisfied equation

(2) (A) if same number or terms is added, substract multiply or divide to both side of equation , the equation remain same (elemination method)
3x+5=8
3x=3(deduct 5 in both side)
X=1 (divid from 3 in both side)
(B) change in the side of required terms.
3x+5= 8
3x= 8-5
3x=3
x = 3/3 = 1

setting unix cron job

*/2 * * * * /opt/script/backup.sh

* * * * * /usr/bin/php /var/www/domain.com/backup.php > /dev/null 2>&1

Setting innodb_lock_wait_timeout

The length of time in seconds an InnoDB transaction waits for a row lock before giving up. The default value is 50 seconds. A transaction that tries to access a row that is locked by another InnoDB transaction waits at most this many seconds for write access to the row before issuing the following error:

ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction

1	ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction

When a lock wait timeout occurs, the current statement is rolled back (not the entire transaction).

to show default value of innodb_lock_wait_timeout we use

show variables like 'innodb_lock_wait_timeout';

1	show variables like 'innodb_lock_wait_timeout';

and for changing the value of innodb_lock_wait_timeout we use following command

SET GLOBAL innodb_lock_wait_timeout = 150;

1	SET GLOBAL innodb_lock_wait_timeout = 150;

Tell me about yourself

This is often the opening question in an interview, be extra careful that you Keep your answer to a minute. You can Cover topics- early years, education, work history, and recent career experience. last subject. this is likely to be a warm-up question.