JavaScript, often abbreviated as JS, is a programming language that conforms to the ECMAScript specification. JavaScript is high-level, often just-in-time compiled, and multi-paradigm. It has curly-bracket syntax, dynamic typing, prototype-based object-orientation, and first-class functions. The of this repo is to save my js programs. Basics of JavaScript. Beginner level.
Most important javascript build in methods
- 1.1 typeof: Returns the type.
console.log(typeof 44); // number console.log(typeof 'something'); // string console.log(typeof true); // boolean let num = 12; console.log(typeof(num)); // number
- 1.2 toString: Returns the string representation of the number's value.
let num = 10; let n = num.toString(); console.log(typeof(num)); // number console.log(typeof(n)); // string
- 1.3 indexOf: Returns the first index at which a given element can be found in the array, or -1 if it is not present.
let str = "Hello world, welcome to the JS Universe."; console.log(str.indexOf("welcome")); // 13 console.log(str.indexOf("wall")); // -1 const fruits = ['Orange', 'Pineapple', 'Apple', 'Melon']; console.log(fruits.indexOf('Melon')); // 3 console.log(fruits.indexOf('klkljkh')); // -1
- 1.4 lastIndexOf: Returns the last index at which a given element can be found in the array, or -1 if it is not present.
const fruits = ['Orange', 'Pineapple', 'Apple', 'Melon']; console.log(fruits.lastIndexOf('Melon')); // 3 console.log(fruits.lastIndexOf('klkljkh')); // -1
- 1.5 length: Returns the number of characters or size in a string or array.
const fruits = ['Orange', 'Pineapple', 'Apple', 'Melon']; console.log(fruits.length); // 4 let str = "Hello world, welcome to the JS Universe."; console.log(str.length); // 40
- 1.6 Interview Qus: Tricky JavaScript Interview Questions and Answers
// remove duplicates form and array let arr = [1, 2, 2, 3, 4]; console.log([...new Set(arr)]); // output test 1 console.log(5 < 6 < 7); // true // 5 < 6 => true => true < 7 => true = 1 => 1 < 7 => true console.log(7 > 6 > 5); // false // 7 > 6 => true => true > 5 => true = 1 => 1 > 5 = false console.log(Math.max()); // -Infinity lowest min number in js console.log(Math.max(1, 2, 3, 4)); // 4 // obj let profile = { name: 'Lakshman' }; // Object.freeze(profile); // freeze don't allow insert and update Object.seal(profile); // freeze don't allow insert, remove but allow update profile.name = 'Gope'; console.log(profile); // obj let user = { name: 'Gope' }; // age not allow any update but name does Object.defineProperty(user, 'age', { value: 4, writable: false }) user.name = 'Lakshman' user.age = 5; console.log(user); // TypeError: Cannot assign to read only property 'age' of object '#<Object>'
- 1.5 rename: Rename multiple files extentions at once by a command (Just for Win).
Get-ChildItem *.css | Rename-Item -NewName { $_.name -Replace '\.css','.scss' }