1: How to remove falsy values from an array?

// Remove falsy values from any array
let miscellaneous = ['🍎', false, '🍊', NaN, 0, undefined, '🌶️', null, '', '🥭'];

// passing Boolean to array.filter() will remove falsy values from array
let fruits = miscellaneous.filter(Boolean);

console.log(fruits); // ['🍎', '🍊', '🌶️', '🥭']

Explanation:

// Boolean(expression) in JS returns true/false
Boolean(5 < 6); //  true
Boolean(100 > 200); // false
Boolean('JavaScript'); //true
Boolean(''); //false

// array example
let miscellaneous = ['🍎', false, '🍊', NaN];
let fruits = miscellaneous.filter(Boolean);

console.log(fruits); // ['🍎', '🍊']

2: How to convert any value to boolean?

// Using !! in front of any value
console.log(!!"mashrafi"); // true
console.log(!!1); // true
console.log(!!0); // false
console.log(!!undefined); // false

// We can also use Boolean() to achieve same
console.log(Boolean("mashrafi")); // true

3: How to resize an array?

// Resizing any array
let animals = ["🐕", "🐒", "🦊", "🐅"];

// We can use array's length property
animals.length = 3;

console.log(animals); // ["🐕", "🐒", "🦊"]

4: How to flatten a multidimensional array?

// How to flattern a multi-dimensional array
let smileys = ['🥰', ['😄', '😃'], '😉', ['🥲', '😑']];

// We can use array.flat() method to flattern one level array
console.log(smileys.flat()); // ['🥰', '😄', '😃', '😉', '🥲', '😑']

// Multi level array
let smileys2 = ['🥰', ['😄', '😃', ['🥲', '😑']], '😉'];

// We can pass 'Infinity' parameter to array.flat function
console.log(smileys2.flat(Infinity)); // ['🥰', '😄', '😃', '🥲', '😑', '😉']

5: How to use short conditionals?

// Short conditionals
const captain = "Mashrafi";

// Instead of doing this
if(captain === "Mashrafi") {
    console.log("❤️");
}

// We can use &&
captain === "Mashrafi" && console.log("❤️");

// And instead of doing this
if(captain !== "Mashrafi") {
    console.log("😡");
}

// We can use ||
captain === "Mashrafi" || console.log("😡");

6: How to replace all occurrences of a string?

// Replace all occurances of a string
const quote = "React is a JS framework & this framework is the most popular front-end framework right now";

// Replace all occurances of 'framework' with 'library'
console.log(quote.replace(/framework/g, "library")); // React is a JS library & this library is the most popular front-end library right now

7: How to log variables with values properly?

// Log values with variable names smartly
const library1 = "jQuery";
const library2 = "React";

// Instead of doing this
console.log(`library1 - ${library1}`); // library1 - jQuery
console.log(`library2 - ${library2}`); // library2 - React

// We can do this
console.log({ library1 }); // {library1: 'jQuery'}
console.log({ library2 }); // {library2: 'React'}

8: How to Know performance of a task

// We can wrap our task with performance.now()
const startTime = performance.now();

for(let i = 0; i <= 50; i++) {
    console.log(i);
}

const endTime = performance.now();

console.log(`loop took ${endTime - startTime} milliseconds to finish`);

Thank you Learn with Sumit Bangladesh for sharing amazing tutorials. Check you the Bangla tutorial #1 JavaScript Tips and Tricks - JavaScript Job Interview Questions - Bangla