Flashcards
Javascript Cheat Sheet
Cards in this deck (33)
- 1Including JavaScript in an HTML Page//JS code goes here
- 2Call an External JavaScript FileIncluding Comments
Single line comments - //
Multi-line comments - /* comment here */ - 3var, const, letvar — 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 — Can not be reassigned and not accessible before they appear
within the code.
let — Similar to const, however, let variable can be reassigned but
not re-declared. - 4Data TypesNumbers — var age = 23
Variables — var x
Text (strings) — var a = "init"
Operations — var b = 1 + 2 + 3
True or fase statements — var c = true
Constant numbers — const PI = 3.14
Objects — var name = {firstName:"John", lastName:”Doe"} - 5Data TypesA letter such as 'A' is a character
A word/phrase like 'Hello' is a string
A number e.g. '2' is an integer
A decimal like '2.9' is real
'yes/no' is Boolean
A phone number '07543988157' is a STRING - 6Objectsvar person = {
firstName:"John",
lastName:"Doe",
age:20,
nationality:"German"
}; - 7Array Methodsconcat() — Join several arrays into one
indexOf() — Returns the primitive value of the specified object
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() — Add a new element at the end
reverse() — Sort elements in descending order
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 first position at which a given element
appears in an array - 8Basic Operators+ — Addition
- — Subtraction
* — Multiplication
/ — Division
(...) — Grouping operator, operations within brackets are executed
earlier than those outside
% — Modulus (remainder )
++ — Increment numbers
-- — Decrement numbers - 9Comparison Operators== — 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 - 10Logical Operators&& — Logical and
|| — Logical or
! — Logical not - 11Bitwise Operators& — AND statement
| — OR statement
~ — NOT
^ — XOR
<< — Left shift
>> — Right shift
>>> — Zero fill right shift - 12FUNCTIONSfunction name(parameter1, parameter2, parameter3) {
// what the function does
} - 13Outputting Dataalert() — 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 - 14Global FunctionsdecodeURI() — 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 - 15JAVASCRIPT LOOPSfor (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 aloop 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 - 16IF - ELSE STATEMENTSif (condition) {
// what to do if condition is met
} else {
// what to do if condition is not met
} - 17STRINGSvar person = "John Doe";
- 18Escape Characters\' — Single quote
\" — Double quote
\\ — Backslash
\b — Backspace
\f — Form feed
\n — New line
\r — Carriage return
\t — Horizontal tabulator
\v — Vertical tabulator - 19String MethodscharAt() — 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 specified 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 lower case
toUpperCase() — Convert strings to upper case
valueOf() — Ret - 20REGULAR EXPRESSION SYNTAX Pattern Modifierse — 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 — Ungreedy pattern - 21Brackets[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 | - 22Metacharacters. — 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 xxx
\xdd — Character specified by a hexadecimal number dd
\uxxxx — The Unicode character specified by a hexadecimal number xxxx - 23Quantifiersn+ — 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 - 24Number PropertiesMAX_VALUE — The maximum numeric value representable in JavaScript
MIN_VALUE — Smallest positive numeric value representable in
JavaScript
NaN — The “Not-a-Number” value
NEGATIVE_INFINITY — The negative Infinity value
POSITIVE_INFINITY — Positive Infinity value - 25Number MethodstoExponential() — 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 - 26Math PropertiesE — Euler’s number
LN2 — The natural logarithm of 2
LN10 — Natural logarithm of 10
LOG2E — Base 2 logarithm of E
LOG10E — Base 10 logarithm of E
PI — The number PI
SQRT1_2 — Square root of 1/2
SQRT2 — The square root of 2 - 27Math Methodsabs(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 - 28Setting DatesDate() — Creates a new date object with the current date and time
Date(2017, 5, 21, 3, 23, 10, 0) — Create a custom date object. The
numbers represent year, month, day, hour, minutes, seconds,
milliseconds. You can omit anything you want except for year and
month.
Date("2017-06-23") — Date declaration as a string - 29Pulling Date and Time ValuesgetDate() — Get the day of the month as a number (1-31)
getDay() — The weekday as a number (0-6)
getFullYear() — Year as a four digit number (yyyy)
getHours() — Get the hour (0-23)
getMilliseconds() — The millisecond (0-999)
getMinutes() — Get the minute (0-59)
getMonth() — Month as a number (0-11)
getSeconds() — Get the second (0-59)
getTime() — Get the milliseconds since January 1, 1970
getUTCDate() — The day (date) of the month in the specified date
according to universal time (also available for day, month, fullyear,
hours, minutes etc.)
parse — Parses a string representation of a date, and returns the
number of milliseconds since January 1, 1970 - 30Set Part of a DatesetDate() — Set the day as a number (1-31)
setFullYear() — Sets the year (optionally month and day)
setHours() — Set the hour (0-23)
setMilliseconds() — Set milliseconds (0-999)
setMinutes() — Sets the minutes (0-59)
setMonth() — Set the month (0-11)
setSeconds() — Sets the seconds (0-59)
setTime() — Set the time (milliseconds since January 1, 1970)
setUTCDate() — Sets the day of the month for a specified date
according to universal time (also available for day, month, fullyear,
hours, minutes etc.) - 31Node Propertiesattributes — Returns a live collection of all attributes registered
to and element
baseURI — Provides the absolute base URL of an HTML element
childNodes — Gives a collection of an element’s child nodes
firstChild — Returns the first child node of an element
lastChild — The last child node of an element
nextSibling — Gives you the next node at the same node tree level
nodeName — Returns the name of a node
nodeType — Returns the type of a node
nodeValue — Sets or returns the value of a node
ownerDocument — The top-level document object for this node
parentNode — Returns the parent node of an element
previousSibling — Returns the node immediately preceding the current
one
textContent — Sets or returns the textual content of a node and its
descendants - 32Node MethodsappendChild() — Adds a new child node to an element as the last child
node
cloneNode() — Clones an HTML element
compareDocumentPosition() — Compares the document position of two
elements
getFeature() — Returns an object which implements the APIs of a
specified feature
hasAttributes() — Returns true if an element has any attributes,
otherwise false
hasChildNodes() — Returns true if an element has any child nodes,
otherwise false
insertBefore() — Inserts a new child node before a specified,
existing child node
isDefaultNamespace() — Returns true if a specified namespaceURI is
the default, otherwise false
isEqualNode() — Checks if two elements are equal
isSameNode() — Checks if two elements are the same node
isSupported() — Returns true if a specified feature is supported on
the element
lookupNamespaceURI() — Returns the namespaceURI associated with a
given node
lookupPrefix() — Returns a DOMString containing the prefix for a
given namespaceURI, if present
normalize() — Joins adjacent text nodes and removes empty text nodes
in an element
removeChild() — Removes a child node from an elem - 33Element MethodsgetAttribute() — Returns the specified attribute value of an element
node
getAttributeNS() — Returns string value of the attribute with the
specified namespace and name
getAttributeNode() — Gets the specified attribute node
getAttributeNodeNS() — Returns the attribute node for the attribute
with the given namespace and name
getElementsByTagName() — Provides a collection of all child elements
with the specified tag name
getElementsByTagNameNS() — Returns a live HTMLCollection of elements
with a certain tag name belonging to the given namespace
hasAttribute() — Returns true if an element has any attributes,
otherwise false
hasAttributeNS() — Provides a true/false value indicating whether the
current element in a given namespace has the specified attribute
removeAttribute() — Removes a specified attribute from an element
removeAttributeNS() — Removes the specified attribute from an element
within a certain namespace
removeAttributeNode() — Takes away a specified attribute node and
returns the removed node
setAttribute() — Sets or changes the specified attribute to a
specified value
setA
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- Cheat Sheet
- Created by
- Jacob Garcia Acosta
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- Created by Jaimee-Lee Kirby · Oct 21, 2015
- Copied by Jacob Garcia Acosta · Feb 4, 2019
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