STRING METHODS: String.charAt | String.charCodeAt | String.endsWith | String.includes | String.indexOf | String.lastIndexOf | String.match | String.matchAll | String.padEnd | String.padStart | String.repeat | String.replace | String.replaceAll | String.search | String.slice | String.split | String.startsWith | String.substring | String.substr | String.toLowerCase | String.toUpperCase | String.toString | String.trim | String.charAt | String.trimEnd | String.trimStart
ARRAYS METHODS:
ADDING: .push() | .unshift() | .splice() | REORGANIZING: .copyWithin() | .slice() | .splice() | COMBINING: .concat() | ... | REMOVING: .pop() | .shift() | .splice() | FILTERING/SEARCHING: .filter() | .find() | .findIndex() | .indexOf() | .lastIndexOf() | SORTING: .sort() | LOOP STRUCTURES: .map() | .flatMap() | .forEach() | .reduce() | BOOLEANS: .every() | .some() | .includes() | CREATING: Array.of() | Array.from() | .fill() | MORPHING: .entries() | .values() | .keys() | .join() | .toString() | .toLocalString() | INFORMATION: .at() - ⚠ Experimental technology! | .length() | Array.isArray() | MISC: .flat() | .reverse() |
OPERATORS: Basic operators | Comparison operators | Logical operators | Bitwise operators | Arithmetic |
REGULAR EXPRESSIONS: Patern modifiers | Brackets | Metacharacters | Quantifiers |
NUMBERS AND MATH: Numbers | Math |
// Returns a string representing the character at the given index.
let str = "Hello World";
str.charAt(0); // "H"// Returns a number representing the UTF-16 code unit value of the character at the given index.
let str = "Hello World";
str.charCodeAt(0); // 72// Returns a new string containing the concatenation of the given strings.
let str = "Hello";
let str2 = " World";
str.concat(str2); // "Hello World"
console.log(`${str}${str2}`); // "Hello World"
console.log(str + str2); // "Hello World"// Returns true if the string ends with the given string, otherwise false.
let str = "Hello World";
str.endsWith("World"); // true// Returns true if the string contains the given string, otherwise false.
let str = "Hello World";
str.includes("World"); // true// Returns the index within the string of the first occurrence of the specified value, or -1 if not found.
let str = "Hello World";
str.indexOf("World"); // 6// Returns the index within the string of the last occurrence of the specified value, or -1 if not found.
let str = "Hello World";
str.lastIndexOf("World"); // 6// Returns a list of matches of a regular expression against a string.
let str = "Hello World";
str.match(/[A-Z]/); // ["H"]// Returns a list of matches of a regular expression against a string.
let str = "Hello World";
str.matchAll(/[A-Z]/g); // ["H", "W"]
// OR
str.match(/[A-Z]/gi); // ["H", "W"]
// /g is global
// /gi is global and case-insensitive// Returns a new string with some content padded to the end of the string.
let str = "Hello";
str.padEnd(14, "World"); // "HelloWorldWorl"// Returns a new string with some content padded to the start of the string.
let str = "Hello";
str.padStart(12, "World"); // "WorldWoHello"// Returns a new string that contains the specified number of copies of the string.
let str = "Hello";
str.repeat(3); // "HelloHelloHello"// Returns a new string with some or all matches of a regular expression replaced by a replacement string.
let str = "Hello World";
str.replace("l", "*"); // "He*lo World"// Returns a new string with some or all matches of a regular expression replaced by a replacement string.
let str = "Hello World";
str.replaceAll("l", "*"); // "He**o Wor*d"
OR;
str.replace(/l/g, "*"); // "He**o Wor*d"// Returns the index within the string of the first occurrence of the specified value, or -1 if not found.
let str = "Hello World 1";
let regex = /[^\D\s]/g; // Find digit
str.search(regex); // 12Check Regular Expressions Check Regular Expressions HERE
// Returns a new string containing the characters of the string from the given index to the end of the string.
let str = "Hello World";
str.slice(6); // "World"// Returns an array of strings split at the given index.
let str = "Hello World";
str.split(" "); // ["Hello", "World"]// Returns true if the string starts with the given string, otherwise false.
let str = "Hello World";
str.startsWith("Hello"); // true// Returns a new string containing the characters of the string from the given index to the end of the string.
let str = "Hello World";
str.substring(1, 2); // "e"// Returns a new string containing the characters of the string from the given index to the end of the string.
let str = "Hello World";
str.substr(1, 2); // "el"NOTE: substr takes parameters as (from, length).
// Returns a new string with all the uppercase characters converted to lowercase.
let str = "Hello World";
str.toLowerCase(); // "hello world"// Returns a new string with all the lowercase characters converted to uppercase.
let str = "Hello World";
str.toUpperCase(); // "HELLO WORLD"// Returns the string representation of the specified object.
let str = new String("Hello World");
console.log(str); // Object of String
str.toString(); // "Hello World"// Returns a new string with the leading and trailing whitespace removed.
let str = " Hello World ";
str.trim(); // "Hello World"// Returns a new string with the trailing whitespace removed.
let str = " Hello World ";
str.trimEnd(); // " Hello World"// Returns a new string with the leading whitespace removed.
let str = " Hello World ";
str.trimStart(); // "Hello World "// Add anything to the end of an array.
let a = []
let b = {}
a.push(b)
console.log(a[0] === b) // true
// Add more than one item at a time.
let x = ['a']
x.push('b', 'c')
console.log(x) // ['a', 'b', 'c']// Add to the beginning of array and returns the new length of the array.
let x = ['c', 'd']
x.unshift('a', 'b') // 4
console.log(x) // ['a', 'b', 'c', 'd']// Add element to an arbitrary location (second param 0).
let a = [1, 2, 3, 4]
a.splice(2, 0, 'foo')
console.log(a) // [1, 2, "foo", 3, 4]// Copy part of an array to another location within the same array.
let a = ['a', 'b', 'c', 'd', 'e']
// target, start, end
array1.copyWithin(0, 3, 4)
console.log(a) // ["d", "b", "c", "d", "e"]// Returns a portion of an array selected with the start and end parameters.
let a = ['ant', 'bison', 'camel', 'duck', 'elephant']
console.log(animals.slice(2)) // ["camel", "duck", "elephant"]
console.log(animals.slice(2, 4)) // ["camel", "duck"]// Replace an arbitrary element in array (second param 1).
let a = [1, 2, 3, 4]
a.splice(2, 1, 'foo')
console.log(a) // [1, 2, "foo", 4]// Create a new array from two arrays.
let x = ['a', 'b', 'c']
let y = ['d', 'e', 'f']
let z = x.concat(y)
console.log(z) // ['a', 'b', 'c', 'd', 'e', 'f']// Not a method, but create a new array from two arrays by spreading them.
let x = ['a', 'b']
let y = ['c', 'd']
let z = [...x, ...y]
console.log(z) // ['a', 'b', 'c', 'd']// Removes the last element from array and returns it. Changes the length of the array.
let a = ['a', 'b', 'c']
console.log(a.pop()) // c
console.log(a) // ["a", "b"]// Like pop but removes the first element from array and returns it. Also changes the length of the array.
let a = ['a', 'b', 'c']
console.log(a.shift()) // a
console.log(a) // ["b", "c"]// Remove elements from the middle of an array. Param 1: index to start removing. Param 2: index to stop removing.
let a = ['a', 'b', 'c', 'd', 'e']
a.splice(1, 3)
console.log(a) // ["a", "e"]// Keeps the items in the array that pass the test provided by the callback function.
let a = ['foo', 'bar', 'fooz']
let b = a.filter(v => v.startsWith('foo'))
console.log(b) // ['foo', 'fooz']// Finds the first item in an array that matches.
let a = [5, 12, 8, 130, 44]
let b = a.find(v => v > 10)
console.log(b) // 12// Like find but instead of returning the item, it returns the index.
let a = [5, 12, 8, 130, 44]
let b = a.findIndex(v => v > 13)
console.log(b) // 3// Finds the first index of an element. Returns -1 if not found.
let a = ['foo', 'bar', 'baz']
console.log(a.indexOf('baz')) // 2
console.log(a.indexOf('quix')) // -1// Like indexOf, but finds the last index of an element. Returns -1 if not found.
let a = ['foo', 'bar', 'baz', 'foo']
console.log(a.lastIndexOf('foo')) // 3
console.log(a.lastIndexOf('quix')) // -1// Sort alphabetically.
let a = ['d', 'j', 'a', 'b', 'c', 'g']
a.sort()
console.log(a) // ["a", "b", "c", "d", "g", "j"]
// Sort in reversed alphabetical order.
let a = ['d', 'j', 'a', 'b', 'c', 'g']
a.sort().reverse()
console.log(a) // [ "j", "g", "d", "c", "b", "a"]
// Sort numerically.
let a = [5, 10, 7, 1, 3, 2]
a.sort((a, b) => a - b)
console.log(a) // [ 1, 2, 3, 5, 7, 10]
// Descending numerical sort (flip the `a` anb `b` around).
let a = [5, 10, 7, 1, 3, 2]
a.sort((a, b) => b - a)
console.log(a) // [10, 7, 5 ,3, 2, 1]// Maps an array to another array by executing a callback function on each element.
let a = [1, 2, 3, 4]
let b = a.flatMap(v => [v * 2])
console.log() // 2, 4, 6, 8// Same as map but it flattens the array, same as: [[]].map(v => v).flat().
let a = [1, 2, 3, 4]
let b = a.map(v => v * 2)
console.log(b) // 2, 4, 6, 8// Executes a function for every element in array, does not return anything.
let a = [1, 2]
a.forEach(x => console.log(x))
// 1
// 2// Executes a user-supplied “reducer” callback function on each element of the array, in order, passing in the return value from the calculation on the preceding element.
let a = [1, 2, 3, 4]
let b = a.reduce((acc, v) => acc + v)
// Basically: 1 + 2 + 3 + 4
console.log(b) // 10
// Return object from an array method.
let a = [1, 2, 3, 4]
let b = a.reduce((acc, v) => ({ [v]: v, ...acc }), {})
console.log(b) // {"1": 1,"2": 2,"3": 3,"4": 4}// Tests if every item in the array passes the test.
let isBelow = v => v < 40
let a = [1, 30, 39, 29, 10, 13]
console.log(a.every(isBelow)) // true// Tests if some items in the array passes the test.
let isOver = v => v > 40
let a = [1, 30, 41, 29, 10, 13]
console.log(a.some(isOver)) // true// Tests if some items in the array passes the test.
let a = [1, 2, 3]
let b = a.includes(2)
console.log(b) // true// Creates a new array from the given arguments.
Array.of('foo', 'bar')
// ['foo', 'bar']// Creates a new array from an array-like or iterable object.
console.log(Array.from('foo')) // ['f', 'o', 'o']
console.log(Array.from([1, 2, 3], x => x + x)) // [2, 4, 6]// Change all elements in an array to a static value.
let a = [1, 2, 3, 4]
let b = a.fill(0, 2, 4)
console.log(b) // [1, 2, 0, 0]// Returns an iterator object with key/value pairs for each index in the array.
let a = ['a', 'b', 'c']
let iterator = a.entries()
console.log(iterator.next().value) // [0, "a"]
console.log([...iterator]) // [[0, "a"], [1, "b"], [2, "c"]]`]// Returns an iterator object with values for each index in the array. Changes the data type from array to iterator.
let a = ['a', 'b', 'c']
let iterator = a.values()
for (const v of iterator) { console.log(v) } // a, b, c// Returns an iterator object with keys for each index in the array. Changes the data type from array to iterator.
let a = ['a', 'b', 'c']
let iterator = a.keys()
for (const v of iterator) { console.log(v) } // 1, 2, 3// Turn array into a string by joining the element togethe
let a = ['foo', 'bar', 'baz']
a.join() // foo,bar,baz
a.join('-') // foo-bar-baz// Turn array or any other object into a string.
let a = ['foo', 'bar', 'baz']
a.toString() // foo,bar,baz// Stringifies an array in a locale sensitive way.
let a = [1, 'a', new Date('21 Dec 1997 14:12:00 UTC')]
a.toLocaleString('en', { timeZone: 'UTC' }) // 1,a,12/21/1997, 2:12:00 PM
a.toLocaleString('de') // '1,a,21.12.1997, 15:12:00'
// toLocaleString(locales, options).toLocalString() - Parameter Values
// Takes in integer value and returns the array element at that index. -1 returns the last element. ⚠️ Experimental technology.
let x = ['a', 'b', 'c']
console.log(a.at(1)) // b
console.log(a.at(-1)) // c// Gets the element count of an array.
let x = ['a', 'b', 'c']
console.log(a.length) // 3// Tests if a given variable is an array.
let a = ['a', 'b']
console.log(Array.isArray(a)) // true// Flatten a nested array.
let a = [0, 1, 2, [3, 4]]
let b = a.flat()
console.log(b) // [0, 1, 2, 3, 4]// Reverses the order of an array.
let a = [1, 2, 3, 4]
a.reverse()
console.log(a) // [4, 3, 2, 1]+ // Addition
- // Subtraction
* // Multiplication
/ // Division
(..) // Grouping operator
% // Modulus (remainder)
++ // Increment numbers
-- // Decrement numbers
== // 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
&& // Logical and
|| // Logical or
! // Logical not
& // AND statement
| // OR statement
~ // NOT
^ // XOR
<< // Left shift
>> // Right shift
>>> // Zero fill right shift
a * (b + c) // grouping
person.age // member
person[age] // member
!(a == b) // logical not
a != b // not equal
typeof a // type (number, object, function...)
x << 2 x >> 3 // minary shifting
a = b // assignment
a == b // equals
a != b // unequal
a === b // strict equal
a !== b // strict unequal
a < b a > b // less and greater than
a <= b a >= b // less or equal, greater or eq
a += b // a = a + b (works with - * %...)
a && b // logical and
a || b // logical or
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
[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 |
. // 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
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
let pi = 3.141;
pi.toFixed(0); // returns 3
pi.toFixed(2); // returns 3.14 - for working with money
pi.toPrecision(2) // returns 3.1
pi.valueOf(); // returns number
Number(true); // converts to number
Number(new Date()) // number of milliseconds since 1970
parseInt("3 months"); // returns the first number: 3
parseFloat("3.5 days"); // returns 3.5
Number.MAX_VALUE // largest possible JS number
Number.MIN_VALUE // smallest possible JS number
Number.NEGATIVE_INFINITY // -Infinity
Number.POSITIVE_INFINITY // Infinity
let pi = Math.PI; // 3.141592653589793
Math.round(4.4); // 4 - rounded
Math.round(4.5); // 5
Math.pow(2,8); // 256 - 2 to the power of 8
Math.sqrt(49); // 7 - square root
Math.abs(-3.14); // 3.14 - absolute, positive value
Math.ceil(3.14); // 4 - rounded up
Math.floor(3.99); // 3 - rounded down
Math.sin(0); // 0 - sine
Math.cos(Math.PI); // OTHERS: tan,atan,asin,acos,
Math.min(0, 3, -2, 2); // -2 - the lowest value
Math.max(0, 3, -2, 2); // 3 - the highest value
Math.log(1); // 0 natural logarithm
Math.exp(1); // 2.7182pow(E,x)
Math.random(); // random number between 0 and 1
Math.floor(Math.random() * 5) + 1; // random integer, from 1 to 5