Hey everyone! I've got some great news for all you beginners learning JavaScript! A quick reference guide for JavaScript is now available! You can easily check important concepts, functions, and methods right away. For more details about the guide, check it out here.
What's in the Quick Reference Guide
Console
// => Hello world!
console.log("Hello world!");
// => Hello CheatSheets.zip
console.warn("hello %s", "CheatSheets.zip");
// Output error message to standard error
console.error(new Error("Oops!"));
Numbers
let amount = 6;
let price = 4.99;
Variables
let x = null;
let name = "Tammy";
const found = false;
// => Tammy, false, null
console.log(name, found, x);
var a;
console.log(a); // => undefined
Strings
let single = "Wheres my bandit hat?";
let double = "Wheres my bandit hat?";
// => 21
console.log(single.length);
Arithmetic Operators
5 + 5 = 10 // Addition
10 - 5 = 5 // Subtraction
5 * 10 = 50 // Multiplication
10 / 5 = 2 // Division
10 % 5 = 0 // Modulus
Comments
// This is a comment
/*
You need to change this setting
before deployment.
*/
Assignment Operators
let number = 100;
// Both statements add 10
number = number + 10;
number += 10;
console.log(number);
// => 120
String Interpolation
let age = 7;
// String concatenation
"Tommy is " + age + " years old.";
// String interpolation
`Tommy is ${age} years old.`;
Conditional Statements
const isMailSent = true;
if (isMailSent) {
console.log("Mail sent to recipient");
}
Ternary Operator
var x = 1;
// => true
result = x == 1 ? true : false;
Logical Operators
true || false; // true
10 > 5 || 10 > 20; // true
false || false; // false
10 > 100 || 10 > 20; // false
Comparison Operators
1 > 3; // false
3 > 1; // true
250 >= 250; // true
1 === 1; // true
1 === 2; // false
1 === "1"; // false
Arrays
const fruits = ["apple", "orange", "banana"];
// Different data types
const data = [1, "chicken", false];
Objects
const apple = {
color: "Green",
price: { bulk: "$3/kg", smallQty: "$4/kg" },
};
console.log(apple.color); // => Green
console.log(apple.price.bulk); // => $3/kg
Classes
class Dog {
constructor(name) {
this._name = name;
}
introduce() {
console.log("This is " + this._name + " !");
}
// Static method
static bark() {
console.log("Woof!");
}
}
const myDog = new Dog("Buster");
myDog.introduce();
// Calling static method
Dog.bark();
Modules
// myMath.js
// Default export
export default function add(x, y) {
return x + y;
}
// Named export
export function subtract(x, y) {
return x - y;
}
// Multiple exports
function multiply(x, y) {
return x * y;
}
function duplicate(x) {
return x * 2;
}
export { multiply, duplicate };
Asynchronous Processing
function helloWorld() {
return new Promise((resolve) => {
setTimeout(() => {
resolve("Hello World!");
}, 2000);
});
}
async function msg() {
const msg = await helloWorld();
console.log("Message:", msg);
}
msg(); // Message: Hello World! <-- after 2 seconds
This quick reference guide covers a wide range of topics from the basics to more advanced JavaScript concepts. Be sure to download it here and make it a handy tool for your coding journey!
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