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.
Thank you For Reading🤩 Subscribe to our newsletter , we send it occasionally with amazing news, resources and many thing.
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; // Number
var name = "Sam"; // string
var name = {first:"Sam", last:"Singh"}; // object
var truth = false; // boolean
var sheets = ["HTML", "CSS", "JS"]; // array
var a; typeof a; // undefined
var a = null; // value null
JavaScript Operators Cheat Sheet
a = b + c - d; // addition, substraction
a = b * (c / d); // multiplication, division
x = 100 % 48; // modulo. 100 / 48 remainder = 4
a++; 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; // variable
var b = "init"; // string
var c = "Hi" + "" + "Sam"; // "Hi Sam"
var d = 1 + 2 + "3"; // "33"
var e = [2,3,5,8]; // array
var f = false; // boolean
var g = /()/; // RegEx
var h = function(){}; // function object
const PI = 3.14; // constant
var a = 1, b = 2, c = a + b; // one line
let 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⚡
Thank you For Reading🤩 Subscribe to our newsletter , we send it occasionally with amazing news, resources and many thing.
Top comments (0)