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May 29, 2021 07:05 am GMT

The ultimate JavaScript cheatsheet you'll ever need

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.

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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

toFixed() : formats a number using fixed-point notation

  function financial(x) {      return Number.parseFloat(x).toFixed(2);   }  console.log(financial(123.456));   // -> 123.46

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

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

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

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

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,

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,

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,

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,

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

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

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

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

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

trim() : Removes whitespace from both ends of a string

  const greeting = "  Hello world!   ";   console.log(greeting);   // -> Hello world!  console.log(greeting.trim());   // -> Hello world!

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

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.

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" ]

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

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

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"]

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" ]

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 ]

sort() : Sorts the element of an array

  let months = ["March", "Jan", "Feb", "Dec"];   months.sort();   console.log(months);   // -> Array(4) [ "Dec", "Feb", "Jan", "March" ]

toString() : Converts an array to string, and returns the result

  const array1 = [1, 2, "a", "1a"];   console.log(array1.toString());   // -> 1,2,a,1a

JavaScript Datatypes Cheat Sheet

var age = 18; // Numbervar name = "Sam"; // stringvar name = {first:"Sam", last:"Singh"}; // objectvar truth = false; // booleanvar sheets = ["HTML", "CSS", "JS"]; // arrayvar a; typeof a; // undefined var a = null; // value null

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

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" + "" + "Sam"; // "Hi Sam"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

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

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.getMonth()); // (January gives 0)  // -> 6

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

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

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

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

Thanks For Reading | Happy Coding

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