Useful Javascript Tricks

1-25

Trick	Purpose	Syntax	Example
Trick 1	Remove duplicates from an array	Array.from(new Set(array))	const uniqueArray = Array.from(new Set([1, 2, 2, 3]))
Trick 2	Check if a variable is defined	typeof variable !== 'undefined'	javascript if (typeof myVar !== 'undefined') { /* do something */ }
Trick 3	Create an array with a range of numbers	Array.from({ length: n }, (_, i) => i)	const numbers = Array.from({ length: 5 }, (_, i) => i);
Trick 4	Convert an array-like object to an array	Array.from(arrayLike)	const arrayLike = { 0: 'one', 1: 'two', length: 2 }; const newArray = Array.from(arrayLike);
Trick 5	Merge two objects	const merged = { ...obj1, ...obj2 }	javascript const obj1 = { a: 1, b: 2 }; const obj2 = { b: 3, c: 4 }; const merged = { ...obj1, ...obj2 };
Trick 6	Shuffle an array	array.sort(() => Math.random() - 0.5)	javascript const shuffledArray = array.sort(() => Math.random() - 0.5);
Trick 7	Check if a string contains a substring	string.includes(substring)	const contains = 'Hello, world!'.includes('world');
Trick 8	Get the current date in ISO format	const isoDate = new Date().toISOString();	const isoDate = new Date().toISOString();
Trick 9	Find the maximum number in an array	const max = Math.max(...array)	const numbers = [3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5]; const max = Math.max(...numbers);
Trick 10	Check if an array is empty	const isEmpty = array.length === 0;	const isEmpty = [].length === 0;
Trick 11	Flatten a nested array	const flatArray = nestedArray.flat();	const nestedArray = [1, [2, 3], [4, [5, 6]]]; const flatArray = nestedArray.flat(Infinity);
Trick 12	Convert a string to uppercase	const uppercased = string.toUpperCase();	const string = 'hello'; const uppercased = string.toUpperCase();
Trick 13	Convert a string to lowercase	const lowercased = string.toLowerCase();	const string = 'Hello'; const lowercased = string.toLowerCase();
Trick 14	Replace all occurrences of a substring	const replaced = string.replace(/old/g, 'new');	const string = 'old text old text'; const replaced = string.replace(/old/g, 'new');
Trick 15	Check if an object is empty	const isEmpty = Object.keys(obj).length === 0;	const isEmpty = Object.keys({}).length === 0;
Trick 16	Convert a string to an array of characters	const charArray = string.split('');	const string = 'hello'; const charArray = string.split('');
Trick 17	Get the last element of an array	const lastElement = array[array.length - 1];	const array = [1, 2, 3, 4, 5]; const lastElement = array[array.length - 1];
Trick 18	Generate a random number within a range	const randomNum = Math.floor(Math.random() * (max - min + 1)) + min;	const min = 1; const max = 10; const randomNum = Math.floor(Math.random() * (max - min + 1)) + min;
Trick 19	Reverse a string	const reversed = string.split('').reverse().join('');	const string = 'hello'; const reversed = string.split('').reverse().join('');
Trick 20	Check if an array contains a specific value	const containsValue = array.includes(value);	const array = [1, 2, 3, 4, 5]; const value = 3; const containsValue = array.includes(value);
Trick 21	Find the index of an element in an array	const index = array.indexOf(element);	const array = [1, 2, 3, 4, 5]; const element = 3; const index = array.indexOf(element);
Trick 22	Convert a number to a string with leading zeros	const strWithZeros = num.toString().padStart(width, '0');	const num = 42; const strWithZeros = num.toString().padStart(4, '0');
Trick 23	Swap the values of two variables	let temp = a; a = b; b = temp;	javascript let a = 1; let b = 2; let temp = a; a = b; b = temp;
Trick 24	Truncate a string to a specified length	const truncated = string.slice(0, maxLength);	const string = 'This is a long string'; const maxLength = 10; const truncated = string.slice(0, maxLength);
Trick 25	Calculate the factorial of a number	function factorial(n) { return n <= 1 ? 1 : n * factorial(n - 1); }	const result = factorial(5);

26-50

Trick	Purpose	Syntax	Example
Trick 26	Convert a string to a number	const num = parseFloat(string);	const string = '3.14'; const num = parseFloat(string);
Trick 27	Capitalize the first letter of a string	const capitalized = string.charAt(0).toUpperCase() + string.slice(1);	const string = 'hello'; const capitalized = string.charAt(0).toUpperCase() + string.slice(1);
Trick 28	Check if an element exists in the DOM	const elementExists = !!document.querySelector(selector);	const elementExists = !!document.querySelector('.my-element');
Trick 29	Convert an object to a JSON string	const jsonString = JSON.stringify(obj);	const obj = { name: 'John', age: 30 }; const jsonString = JSON.stringify(obj);
Trick 30	Parse a JSON string to an object	const obj = JSON.parse(jsonString);	const jsonString = '{"name":"John","age":30}'; const obj = JSON.parse(jsonString);
Trick 31	Sort an array of objects by a property	array.sort((a, b) => a.property - b.property);	javascript const people = [{ name: 'Alice', age: 25 }, { name: 'Bob', age: 30 }]; people.sort((a, b) => a.age - b.age);
Trick 32	Get the current URL	const currentURL = window.location.href;	const currentURL = window.location.href;
Trick 33	Execute a function after a delay	setTimeout(() => { /* code to execute */ }, delayInMilliseconds);	javascript setTimeout(() => { console.log('Delayed function executed!'); }, 2000);
Trick 34	Remove whitespace from a string	const trimmed = string.replace(/\s+/g, '');	const string = ' Hello, world! '; const trimmed = string.replace(/\s+/g, '');
Trick 35	Get the current timestamp (milliseconds)	const timestamp = Date.now();	const timestamp = Date.now();
Trick 36	Calculate the difference between two dates	const differenceInDays = Math.floor((date2 - date1) / (1000 * 60 * 60 * 24));	javascript const date1 = new Date('2023-09-01'); const date2 = new Date('2023-09-10'); const differenceInDays = Math.floor((date2 - date1) / (1000 * 60 * 60 * 24));
Trick 37	Check if a number is an integer	const isInteger = Number.isInteger(num);	const num = 42; const isInteger = Number.isInteger(num);
Trick 38	Get the current day of the week	const dayOfWeek = new Date().getDay();	const dayOfWeek = new Date().getDay();
Trick 39	Find the smallest number in an array	const min = Math.min(...array);	const numbers = [3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5]; const min = Math.min(...numbers);
Trick 40	Convert an array to a comma-separated string	const csvString = array.join(',');	const array = ['apple', 'banana', 'cherry']; const csvString = array.join(',');
Trick 41	Get the current time in HH format	const time = new Date().toLocaleTimeString('en-US', { hour: '2-digit', minute: '2-digit' });	const time = new Date().toLocaleTimeString('en-US', { hour: '2-digit', minute: '2-digit' });
Trick 42	Create a copy of an array	const copy = array.slice();	const originalArray = [1, 2, 3]; const copy = originalArray.slice();
Trick 43	Calculate the square root of a number	const sqrt = Math.sqrt(num);	const num = 16; const sqrt = Math.sqrt(num);
Trick 44	Check if a function is defined	const isDefined = typeof func === 'function';	const isDefined = typeof myFunction === 'function';
Trick 45	Generate a random hexadecimal color	const randomColor = '#' + Math.floor(Math.random()*16777215).toString(16);	const randomColor = '#' + Math.floor(Math.random()*16777215).toString(16);
Trick 46	Convert a string to title case	`const titleCase = string.toLowerCase().replace(/^(.)	\s+(.)/g, ($1) => $1.toUpperCase());`
Trick 47	Check if an array contains only unique values	const isUnique = array.length === new Set(array).size;	const array = [1, 2, 3, 4, 5]; const isUnique = array.length === new Set(array).size;
Trick 48	Get the current month	const currentMonth = new Date().getMonth() + 1;	const currentMonth = new Date().getMonth() + 1;
Trick 49	Get a random item from an array	const randomItem = array[Math.floor(Math.random() * array.length)];	const array = [1, 2, 3, 4, 5]; const randomItem = array[Math.floor(Math.random() * array.length)];
Trick 50	Convert a string with spaces to kebab case	const kebabCase = string.replace(/\s+/g, '-').toLowerCase();	const string = 'This is a Test String'; const kebabCase = string.replace(/\s+/g, '-').toLowerCase();

51-75

Trick	Purpose	Syntax	Example
Trick 51	Check if a string starts with a substring	const startsWith = string.startsWith(substring);	const string = 'Hello, world!'; const startsWith = string.startsWith('Hello');
Trick 52	Check if a string ends with a substring	const endsWith = string.endsWith(substring);	const string = 'Hello, world!'; const endsWith = string.endsWith('world!');
Trick 53	Convert a number to a binary string	const binaryString = num.toString(2);	const num = 42; const binaryString = num.toString(2);
Trick 54	Check if a string is empty or contains only whitespace	const isEmptyOrWhitespace = string.trim() === '';	const string = ' '; const isEmptyOrWhitespace = string.trim() === '';
Trick 55	Check if an array contains a specific object	const containsObject = array.some(item => item === object);	const array = [{ id: 1 }, { id: 2 }, { id: 3 }]; const object = { id: 2 }; const containsObject = array.some(item => item.id === object.id);
Trick 56	Get the first N elements of an array	const firstN = array.slice(0, N);	const array = [1, 2, 3, 4, 5]; const firstN = array.slice(0, 3);
Trick 57	Get the last N elements of an array	const lastN = array.slice(-N);	const array = [1, 2, 3, 4, 5]; const lastN = array.slice(-3);
Trick 58	Swap the values of two objects	javascript const temp = {...obj1}; Object.assign(obj1, obj2); Object.assign(obj2, temp);	javascript const obj1 = { a: 1, b: 2 }; const obj2 = { b: 3, c: 4 }; const temp = { ...obj1 }; Object.assign(obj1, obj2); Object.assign(obj2, temp);
Trick 59	Remove an element from an array by value	array = array.filter(item => item !== value);	let array = [1, 2, 3, 4, 5]; const value = 3; array = array.filter(item => item !== value);
Trick 60	Check if an array is a subset of another array	const isSubset = subset.every(item => array.includes(item));	const array = [1, 2, 3, 4, 5]; const subset = [2, 3]; const isSubset = subset.every(item => array.includes(item));
Trick 61	Find the index of the maximum value in an array	const maxIndex = array.indexOf(Math.max(...array));	const array = [3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5]; const maxIndex = array.indexOf(Math.max(...array));
Trick 62	Calculate the average of an array	const average = array.reduce((acc, val) => acc + val, 0) / array.length;	const array = [1, 2, 3, 4, 5]; const average = array.reduce((acc, val) => acc + val, 0) / array.length;
Trick 63	Reverse the order of words in a string	const reversedWords = string.split(' ').reverse().join(' ');	const string = 'Hello, world!'; const reversedWords = string.split(' ').reverse().join(' ');
Trick 64	Convert a number to currency format	const currencyFormatted = num.toFixed(2);	const num = 42.567; const currencyFormatted = num.toFixed(2);
Trick 65	Create a unique identifier (UUID)	```javascript const uuid = ‘xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx’.replace(/[xy]/g, function(c) { const r = Math.random() * 16	0, v = c == ‘x’ ? r : (r & 0x3
Trick 66	Convert a string with hyphens to camelCase	const camelCase = string.replace(/-([a-z])/g, (_, letter) => letter.toUpperCase());	const string = 'this-is-a-test'; const camelCase = string.replace(/-([a-z])/g, (_, letter) => letter.toUpperCase());
Trick 67	Check if a value is a JavaScript array	const isArray = Array.isArray(value);	const value = [1, 2, 3]; const isArray = Array.isArray(value);
Trick 68	Deep copy an object	const deepCopy = JSON.parse(JSON.stringify(object));	const object = { a: 1, b: { c: 2 } }; const deepCopy = JSON.parse(JSON.stringify(object));
Trick 69	Calculate the length of an object (number of properties)	const length = Object.keys(obj).length;	const obj = { a: 1, b: 2, c: 3 }; const length = Object.keys(obj).length;
Trick 70	Check if an element is visible in the viewport	```javascript const isVisible = (element) => { const rect = element.getBoundingClientRect(); return (rect.top >= 0 && rect.left >= 0 && rect.bottom <= (window.innerHeight
Trick 71	Find the median value in an array	javascript const median = (arr) => { const mid = Math.floor(arr.length / 2), nums = [...arr].sort((a, b) => a - b); return arr.length % 2 !== 0 ? nums[mid] : (nums[mid - 1] + nums[mid]) / 2; };	javascript const numbers = [5, 1, 3, 9, 2]; const median = (arr) => { const mid = Math.floor(arr.length / 2), nums = [...arr].sort((a, b) => a - b); return arr.length % 2 !== 0 ? nums[mid] : (nums[mid - 1] + nums[mid]) / 2; }; median(numbers);
Trick 72	Encode a URL parameter	const encodedParam = encodeURIComponent(param);	const param = 'user input'; const encodedParam = encodeURIComponent(param);
Trick 73	Check if a value is a primitive	const isPrimitive = (value !== Object(value));	const isPrimitive = (42 !== Object(42));
Trick 74	Create an array with a sequence of numbers	const sequence = Array.from({ length: n }, (_, i) => i + start);	const n = 5; const start = 1; const sequence = Array.from({ length: n }, (_, i) => i + start);
Trick 75	Check if a year is a leap year	`const isLeapYear = (year % 4 === 0 && year % 100 !== 0)

76-100

Trick	Purpose	Syntax	Example
Trick 76	Create an array with unique values	const uniqueArray = [...new Set(array)];	const array = [1, 2, 2, 3, 3, 4]; const uniqueArray = [...new Set(array)];
Trick 77	Round a number to a specified decimal place	const rounded = Number(number.toFixed(decimalPlaces));	const number = 3.14159; const decimalPlaces = 2; const rounded = Number(number.toFixed(decimalPlaces));
Trick 78	Convert a string to a date object	const date = new Date(string);	const dateString = '2023-09-17'; const date = new Date(dateString);
Trick 79	Generate a random integer within a range	const randomInt = Math.floor(Math.random() * (max - min + 1)) + min;	const min = 1; const max = 10; const randomInt = Math.floor(Math.random() * (max - min + 1)) + min;
Trick 80	Remove duplicates from an array using a Set	const uniqueArray = [...new Set(array)];	const array = [1, 2, 2, 3, 3, 4]; const uniqueArray = [...new Set(array)];
Trick 81	Get the current year	const currentYear = new Date().getFullYear();	const currentYear = new Date().getFullYear();
Trick 82	Get the current month (zero-based)	const currentMonth = new Date().getMonth();	const currentMonth = new Date().getMonth();
Trick 83	Get the current day of the month	const currentDay = new Date().getDate();	const currentDay = new Date().getDate();
Trick 84	Sort an array of strings alphabetically	const sortedArray = array.sort();	const array = ['banana', 'apple', 'cherry']; const sortedArray = array.sort();
Trick 85	Generate a random color in RGB format	const randomColor = 'rgb(' + Math.floor(Math.random() * 256) + ',' + Math.floor(Math.random() * 256) + ',' + Math.floor(Math.random() * 256) + ')';	const randomColor = 'rgb(' + Math.floor(Math.random() * 256) + ',' + Math.floor(Math.random() * 256) + ',' + Math.floor(Math.random() * 256) + ')';
Trick 86	Check if an element is an array	const isArray = Array.isArray(element);	const element = [1, 2, 3]; const isArray = Array.isArray(element);
Trick 87	Get the current timestamp (seconds)	const timestamp = Math.floor(Date.now() / 1000);	const timestamp = Math.floor(Date.now() / 1000);
Trick 88	Replace all occurrences of a character in a string	const replaced = string.replace(/char/g, 'replacement');	const string = 'a-b-c-d'; const replaced = string.replace(/-/g, '_');
Trick 89	Calculate the distance between two points	javascript const distance = Math.sqrt(Math.pow(x2 - x1, 2) + Math.pow(y2 - y1, 2));	javascript const x1 = 0, y1 = 0, x2 = 3, y2 = 4; const distance = Math.sqrt(Math.pow(x2 - x1, 2) + Math.pow(y2 - y1, 2));
Trick 90	Create a function with default parameters	javascript function greet(name = 'Anonymous') { return `Hello, ${name}!`; }	javascript function greet(name = 'Anonymous') { return `Hello, ${name}!`; } const message = greet('Alice');
Trick 91	Get the current time in HH:MM format	javascript const now = new Date(); const formattedTime = now.toLocaleTimeString('en-US');	javascript const now = new Date(); const formattedTime = now.toLocaleTimeString('en-US');
Trick 92	Check if a value is NaN	const isNaN = Number.isNaN(value);	const value = 'Not a number'; const isNaN = Number.isNaN(value);
Trick 93	Create a random alphanumeric string	javascript const randomString = Math.random().toString(36).substring(2, 10);	javascript const randomString = Math.random().toString(36).substring(2, 10);
Trick 94	Find the index of the minimum value in an array	const minIndex = array.indexOf(Math.min(...array));	const array = [3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5]; const minIndex = array.indexOf(Math.min(...array));
Trick 95	Convert a string to an array of words	const words = string.split(' ');	const string = 'Hello world'; const words = string.split(' ');
Trick 96	Remove leading and trailing whitespace from a string	const trimmed = string.trim();	const string = ' Trim me '; const trimmed = string.trim();
Trick 97	Check if an array contains only truthy values	const isTruthy = array.every(Boolean);	const array = [true, 1, 'hello', 42]; const isTruthy = array.every(Boolean);
Trick 98	Get the current time in milliseconds since epoch	const currentTimeMillis = Date.now();	const currentTimeMillis = Date.now();
Trick 99	Find the index of the first occurrence of an element in an array	const index = array.indexOf(element);	const array = ['apple', 'banana', 'cherry']; const element = 'banana'; const index = array.indexOf(element);
Trick 100	Convert a string to an array of characters	const charArray = [...string];	const string = 'hello'; const charArray = [...string];