January 12, 2021 06:54 am GMT
Original Link: https://dev.to/rahxuls/ultimate-javascript-cheatsheet-for-2021-41f6
Ultimate JavaScript CheatSheet
Cheat Sheets our something developers need always for reference. So here I have compiled many JavaScript reference codes. See the classification and find it. This post is helpful for learners and developers.
JavaScript Number Method Cheat Sheet
- toExponential() : Returns a string representing the Number object in exponential notation
function expo(x, f) { return Number.parseFloat(x).toExponential(f); } console.log(expo(123456, 2)); // -> 1.23e+5
Enter fullscreen mode Exit fullscreen mode
- toFixed() : formats a number using fixed-point notation
function financial(x) { return Number.parseFloat(x).toFixed(2); } console.log(financial(123.456)); // -> 123.46
Enter fullscreen mode Exit fullscreen mode
- toPrecision() : returns a string representing the Number object to the specified precision
function precise(x) { return Number.parseFloat(x).toPrecision(4); } console.log(precise(123.456)); // -> 123.5
Enter fullscreen mode Exit fullscreen mode
- toString() : returns a string representing the specifies Number object
function hexColour(c) { if (c < 256) { return Math.abs(c).toString(16); } return 0; } console.log(hexColour(233)); // -> e9
Enter fullscreen mode Exit fullscreen mode
- valueOf() : returns the wrapped primitive value of a number object
const numObj = new Number(42); console.log(typeof numObj); // -> object const num = numObj.valueOf(); console.log(num); // -> 42 console.log(typeof num); // -> number
Enter fullscreen mode Exit fullscreen mode
JavaScript Loops Cheat Sheets
- For Loop
for (var i = 0; < 10; i++) { console.log(i + ": " + i * 3 + "<br />"); } // -> 0: 0<br /> // -> 1: 3<br /> // -> ... let a = [1, 2, 3]; var sum = 0; for (var i - 0; i <a.length; i++) { sum += a[i]; } // pasing an array console.log(sum); // -> 6
Enter fullscreen mode Exit fullscreen mode
- While Loop
var i = 1; // initialize while (i < 100) { // enters the cycle if statement is true i *= 2; // increment to avoid infinte loop console.log(i + ", "); // output } // 2, // 4, // ... // 128,
Enter fullscreen mode Exit fullscreen mode
- Do While Loop
var i = 1; // initialize while (i < 100) { // enters the cycle asleast once i *= 2; // increment to avoid infinte loop console.log(i + ", "); // output } while (1 < 100); // repeats cycle if statement is true at the end // 2, // 4, // ... // 128,
Enter fullscreen mode Exit fullscreen mode
- Break
for (var i = 0; i < 10; i++) { if (i == 5 ) { break; } // stops and exits the cycle console.log(i + ", "); // Lat output number is 4 } // -> 0, // -> 1, // ... // -> 4,
Enter fullscreen mode Exit fullscreen mode
- Continue
for (var i = 0; i < 10; i++) { if (i == 5 ) { continue; } // skips the rest of the cycle console.log(i + ", "); // skips 5 } // -> 0, // -> 1, // ... // -> 9,
Enter fullscreen mode Exit fullscreen mode
JavaScript String Methods Cheat Sheet
- charAt() : Returns the character at the specified index
const sentence = "Jeff bezos is now the second richest."; const index = 4; console.log(`The character at index ${index} is ${sentence.charAt(index)}`); // The character at index 4 is f
Enter fullscreen mode Exit fullscreen mode
- concat() : Joins two or more strings, and returns a copy of the joined strings
const str1 = "Hello"; cosnt str2 = "World"; console.log(str1.concat(" ", str2)); // -> Hello World console.log(str2.concat(", ", str1)); // -> World, Hello
Enter fullscreen mode Exit fullscreen mode
- replace() : Searches for a match between a substring (or regex) and a string and replaces the matched substring with a new substring
const p = "Talk is cheap. Show me the work. - Someone"; console.log(p.replace("work", "code")); // -> Talk is cheap. Show me the code. - Someone
Enter fullscreen mode Exit fullscreen mode
- search() : Searches for a match between a regex and a string, and returns the position of the match
const paragraph = "The quick brown fox jumps over the lazy dog."; // any character that is not a word character or whitespace const regex = /[^\w\s]/g; console.log(paragraph.search(regex)); // -> 43
Enter fullscreen mode Exit fullscreen mode
- slice() : Extracts a part of a string and returns a new string
const str = "The quick brown fox jumps over the lazy dog."; consolelog(str.slice(31)); // -> the lazy dog console.log(str.slice(4, 19)); // -> quick brown fox
Enter fullscreen mode Exit fullscreen mode
- trim() : Removes whitespace from both ends of a string
const greeting = " Hello world! "; console.log(greeting); // -> Hello world! console.log(greeting.trim()); // -> Hello world!
Enter fullscreen mode Exit fullscreen mode
- substr() : Extracts the character from a string, beginning at a specified start position, and through the specified number of character
const str = "Mozilla"; console.log(str.substr(1, 2)); // -> oz console.log(stre.substr(2)); // -> zilla
Enter fullscreen mode Exit fullscreen mode
- toLowerCase() : Converts a string to lowercase letters
const sentence = "Elon became the richest last night."; console.log(sentence.toLowerCase()); // -> elon became the richest last night.
Enter fullscreen mode Exit fullscreen mode
JavaScript Array Method Cheet sheet
- concat() : Joins two or more arrays, and returns a copy of the joined array
let array1 = ["a", "b", "c"]; let array2 = ["d", "e", "f"]; let array3 = array1.concat(array2); console.log(array3); // -> Array(6) ["a", "b", "c", "d", "e", "f" ]
Enter fullscreen mode Exit fullscreen mode
- indexOf() : Search the array for an element and returns its position
let beasts = ["ant", "bison", "camel", "duck", "bison"]; console.log(beasts.indexOf("bison")); // -> 1 // start from index 2 console.log(beasts.indexOf("bison", 2)); // -> 4
Enter fullscreen mode Exit fullscreen mode
- join() : Joins all elements of an array into a string
let elements = ["Fire", "Air", "Water"]; console.log(elements.join()); // -> Fire,Air,Water console.log(elements.join(" ")); // -> Fire Air Water
Enter fullscreen mode Exit fullscreen mode
- pop() : Removes the last element of an array, and returns that element
let plants = ["broccoli", "cauliflower", "cabbage", "kale", "tomato"]; console.log(plants.pop()); // -> tomato console.log(plants); // -> Array(4) ["brocxoli", "cauliflower", "cabbage", "kale"]
Enter fullscreen mode Exit fullscreen mode
- reverse() : Reverses the order of the elements in an array
let array1 = ["one", "two", "three"]; console.log("array1:", array1); // -> array1: Array(3) [ "one", "two", "three" ] let reversed = array1.reverse(); console.log("reversed", reversed); // -> reversed: Array(3) [ "three", "two", "one" ]
Enter fullscreen mode Exit fullscreen mode
- shift() : Removes the first element of an array, and returns that element
let array1 = [1, 2, 3]; let firstElement = array1.shift(); console.log(array1); // -> Array [ 2, 3 ]
Enter fullscreen mode Exit fullscreen mode
- sort() : Sorts the element of an array
let months = ["March", "Jan", "Feb", "Dec"]; months.sort(); console.log(months); // -> Array(4) [ "Dec", "Feb", "Jan", "March" ]
Enter fullscreen mode Exit fullscreen mode
- toString() : Converts an array to string, and returns the result
const array1 = [1, 2, "a", "1a"]; console.log(array1.toString()); // -> 1,2,a,1a
Enter fullscreen mode Exit fullscreen mode
JavaScript Datatypes Cheat Sheet
var age = 18; // Numbervar name = "Rahul"; // stringvar name = {first:"Rahul", last:"Singh"}; // objectvar truth = false; // booleanvar sheets = ["HTML", "CSS", "JS"]; // arrayvar a; typeof a; // undefined var a = null; // value null
Enter fullscreen mode Exit fullscreen mode
JavaScript Operators Cheat Sheet
a = b + c - d; // addition, substractiona = b * (c / d); // multiplication, divisionx = 100 % 48; // modulo. 100 / 48 remainder = 4a++; b--; // postfix increment and decrement
Enter fullscreen mode Exit fullscreen mode
Variables cheat sheet
- 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, let variable can be reassigned but not re-declared
var a; // variablevar b = "init"; // stringvar c = "Hi" + "" + "Rahul"; // "Hi Rahul"var d = 1 + 2 + "3"; // "33"var e = [2,3,5,8]; // arrayvar f = false; // booleanvar g = /()/; // RegExvar h = function(){}; // function objectconst PI = 3.14; // constantvar a = 1, b = 2, c = a + b; // one linelet z = 'zzz'; // block scope local variable
Enter fullscreen mode Exit fullscreen mode
Get Date Methods Cheet Sheet
- getFullYear() : Returns the year of the specified date according to local time
const moonLanding = new Date("January 08, 69 00:20:10"); console.log(moonLanding.getFullYear()); // -> 1969
Enter fullscreen mode Exit fullscreen mode
- getMonth() : Returns the month in the specified date according to local time, as a zero-based value (where zero indicates the first month of the year).
const moonLanding = new Date("January 08, 69 00:20:10"); console.log(moonLanding.getFullYear()); // (January gives 0) // -> 6
Enter fullscreen mode Exit fullscreen mode
- getDate() : Returns the day of the month for the specified date according to local time
const birthday = new Date("June 16, 2004 23:14:00"); const date1 = birthday.getDate(); console.log(date1); // -> 19
Enter fullscreen mode Exit fullscreen mode
- getHours() : Returns the hour for the specified date, according to local time
const birthday = new Date("June 16, 04 4:20"); console.log(birthday.getHours()); // -> 4
Enter fullscreen mode Exit fullscreen mode
- getMinutes() : Returns the minutes in the specified date according to local time
const birthday = new Date("June 16, 04 04:10"); console.log(birthday.getMinutes()); // -> 20
Enter fullscreen mode Exit fullscreen mode
- getSeconds() Returns the seconds in the specified date according to local time
const moonLanding = newDate("June 16, 69 00:23:11"); console.log(moonLanding.getSeconds()); // -> 18
Enter fullscreen mode Exit fullscreen mode
Hey Guy's subscribe to my weekly newsletter and getting every post link on your mail in the weekend. No daily mails and spamming.
Please subscribe -> Subscribe to RAHULISM
Thanks For Reading | Happy Coding
Original Link: https://dev.to/rahxuls/ultimate-javascript-cheatsheet-for-2021-41f6
Share this article:
Tweet
View Full Article
Dev To
An online community for sharing and discovering great ideas, having debates, and making friendsMore About this Source Visit Dev To