Everything you need to know about JavaScript!!

 When I started learning JS, I used many sources.

And of course I have written few articles on JS functions and methods. So I thought of clubbing the simple tricks and basics for JS in single place.

Lets start with the variables.

1.Variables:

var, const, let

var: The most common variable. Can be reassigned but only accessed within a function. Variables defined with var move to the top when code is executed.

const: Cannot be reassigned and not accessible before they appear within the code.

let: Similar to const, however, the let variable can be reassigned but not re-declared.

2. Array Methods:

• concat(): Join several arrays into one
• indexOf(): Returns the first position at which a given element appears in an array
• join(): Combine elements of an array into a single string and return the string
• lastIndexOf(): Gives the last position at which a given element appears in an array
• pop(): Removes the last element of an array
• push(): Adds a new element at the end
• reverse(): Reverse the order of the elements in an array
• shift(): Remove the first element of an array
• slice(): Pulls a copy of a portion of an array into a new array
• sort(): Sorts elements alphabetically
• splice(): Adds elements in a specified way and position
• toString(): Converts elements to strings
• unshift(): Adds a new element to the beginning
• valueOf(): Returns the primitive value of the specified object

3. Operators:

Basic Operators

Addition

• — Subtraction
• Multiplication
• / Division
• (..) Grouping operator
• % Modulus (remainder)
• ++ Increment numbers
• — Decrement numbers

Comparison Operators

• == Equal to
• — Decrement numbers
• === 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

Logical Operators

• && Logical and ||
• Logical or !
• Logical not

Bitwise Operators

• & AND statement
• OR statement
• ~ NOT
• ^ XOR
• << Left shift
• >>Right shift
• >>> Zero fill right shift

4. Functions:

function name(parameter1, parameter2, parameter3) {    // what the function does  }

Outputting Data

• alert(): Output data in an alert box in the browser window
• confirm(): Opens up a yes/no dialog and returns true/false depending on user click
• console.log(): Writes information to the browser console, good for debugging purposes
• document.write():Write directly to the HTML document
• prompt(): Creates an dialogue for user input

Global Functions

• decodeURI(): Decodes a Uniform Resource Identifier (URI) created by encodeURI or similar
• decodeURIComponent(): Decodes a URI component
• encodeURI(): Encodes a URI into UTF-8
• encodeURIComponent(): Same but for URI components
• eval(): Evaluates JavaScript code represented as a string
• isFinite(): Determines whether a passed value is a finite number
• isNaN(): Determines whether a value is NaN or not
• Number(): Returns a number converted from its argument
• parseFloat(): Parses an argument and returns a floating point number
• parseInt(): Parses its argument and returns an integer

5. Loops:

for (before loop; condition for loop; execute after loop) { // what to do during the loop }

• for: The most common way to create a loop in JavaScript
• while: Sets up conditions under which a loop executes
• do while: Similar to the while loop, however, it executes at least once and performs a check at the end to see if the condition is met to execute again
• break: Used to stop and exit the cycle at certain conditions
• continue: Skip parts of the cycle if certain conditions are met

6. If — Else Statements:

if (condition) {    // what to do if condition is met  } else {    // what to do if condition is not met  }

7. Strings:

var fruit = “Apple”;

Escape Characters

• \’ — Single quote
• \” — Double quote
• \\ — Backslash
• \b — Backspace
• \f — Form feed
• \n — New line
• \r — Carriage return
• \t — Horizontal tabulator
• \v — Vertical tabulator

String Methods

• charAt(): Returns a character at a specified position inside a string
• charCodeAt(): Gives you the unicode of character at that position
• concat(): Concatenates (joins) two or more strings into one
• fromCharCode(): Returns a string created from the specified sequence of UTF-16 code units
• indexOf(): Provides the position of the first occurrence of a specified text within a string
• lastIndexOf(): Same as indexOf() but with the last occurrence, searching backwards
• match(): Retrieves the matches of a string against a search pattern
• replace(): Find and replace specific text in a string
• search(): Executes a search for a matching text and returns its position
• slice():Extracts a section of a string and returns it as a new string
• split(): Splits a string object into an array of strings at a specified position
• substr(): Similar to slice() but extracts a substring depended on a specified number of characters
• substring(): Also similar to slice() but can’t accept negative indices
• toLowerCase(): Convert strings to lowercase
• toUpperCase(): Convert strings to uppercase
• valueOf(): Returns the primitive value (that has no properties or methods) of a string object

8. Regular Expressions:

Pattern Modifiers

e — Evaluate replacement

i — Perform case-insensitive matching

g — Perform global matching

m — Perform multiple line matching

s — Treat strings as single line

x — Allow comments and whitespace in pattern

U — Non Greedy pattern

Brackets

[abc] Find any of the characters between the brackets

[^abc] Find any character not in the brackets

[0–9] Used to find any digit from 0 to 9

[A-z] Find any character from uppercase A to lowercase z

(a|b|c) Find any of the alternatives separated with |

Metacharacters

. — Find a single character, except newline or line terminator

\w — Word character

\W — Non-word character

\d — A digit

\D — A non-digit character

\s — Whitespace character

\S — Non-whitespace character

\b — Find a match at the beginning/end of a word

\B — A match not at the beginning/end of a word

\0 — NUL character

\n — A new line character

\f — Form feed character

\r — Carriage return character

\t — Tab character

\v — Vertical tab character 

\xxx — The character specified by an octal number xx

\xdd — Character specified by a hexadecimal number dd

\uxxxx — The Unicode character specified by a hexadecimal number xxxx

Quantifiers

n+ — Matches any string that contains at least one n

n* — Any string that contains zero or more occurrences of n

n? — A string that contains zero or one occurrences of n

n{X} — String that contains a sequence of X n’s

n{X,Y} — Strings that contains a sequence of X to Y n’s

n{X,} — Matches any string that contains a sequence of at least X n’s

n$ — Any string with n at the end of it

^n — String with n at the beginning of it

?=n — Any string that is followed by a specific string n

?!n — String that is not followed by a specific string n

9. Numbers and Math:

Number Methods

• toExponential(): Returns a string with a rounded number written as exponential notation
• toFixed(): Returns the string of a number with a specified number of decimals
• toPrecision(): String of a number written with a specified length
• toString(): Returns a number as a string
• valueOf(): Returns a number as a number

Math Methods

• abs(x) Returns the absolute (positive) value of x
• acos(x) The arccosine of x, in radians
• asin(x) Arcsine of x, in radians
• atan(x) The arctangent of x as a numeric value
• atan2(y,x) Arctangent of the quotient of its arguments
• ceil(x) Value of x rounded up to its nearest integer
• cos(x) The cosine of x (x is in radians)
• exp(x) Value of Ex
• floor(x) The value of x rounded down to its nearest integer
• log(x) The natural logarithm (base E) of x
• max(x,y,z,…,n) Returns the number with the highest value
• min(x,y,z,…,n) Same for the number with the lowest value
• pow(x,y) X to the power of y
• random() Returns a random number between 0 and 1
• round(x) The value of x rounded to its nearest integer
• sin(x) The sine of x (x is in radians)
• sqrt(x) Square root of x
• tan(x) The tangent of an angle

I hope it will be useful to you all guys!!