Built-in Functions : JavaScript 

Javascript functions (in the place of console.log(), you can use
document.write() see output on browser)

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let num = 1234.5678;
console.log(num.toExponential(2)); // Output: 1.23e+3

let num = 123.456;
console.log(num.toFixed(2)); // Output: 123.46

let num = 1234567.89;
console.log(num.toLocaleString(‘en-US’)); // Output: 1,234,567.89

let num = 123.456;
console.log(num.toPrecision(5)); // Output: 123.46

let num = 123;
console.log(num.toString()); // Output: “123”

let num = 123;
console.log(num.valueOf()); // Output: 123

let str = “Hello World”;
console.log(str.charAt(0)); // Output: “H”

let str = “Hello World”;
console.log(str.charCodeAt(0)); // Output: 72

let str1 = “Hello”;
let str2 = “World”;
console.log(str1.concat(” “, str2)); // Output: “Hello World”

let str = “Hello World”;
console.log(str.indexOf(“World”)); // Output: 6

let str = “Hello World”;
console.log(str.lastIndexOf(“l”)); // Output: 9

let str1 = “Hello”;
let str2 = “hello”;
console.log(str1.localeCompare(str2)); // Output: -1

let str = “Hello World”;
console.log(str.length); // Output: 11

let str = “The quick brown fox jumps over the lazy dog”;
console.log(str.match(/the/gi)); // Output: [“the”, “the”]

let str = “Hello World”;
console.log(str.replace(“World”, “Universe”)); // Output: “Hello
Universe”

let str = “The quick brown fox jumps over the lazy dog”;
console.log(str.search(“fox”)); // Output: 16

let str = “Hello World”;
console.log(str.slice(0, 5)); // Output: “Hello”

let str = “Hello World”;
console.log(str.split(” “)); // Output: [“Hello”, “World”]

let str = “Hello World”;
console.log(str.substr(6, 5)); // Output: “World”

let str = “Hello World”;
console.log(str.substring(6, 11)); // Output: “World”

let str = “Hello WORLD”;
console.log(str.toLocaleLowerCase()); // Output: “hello world”

let str = “Hello World”;
console.log(str.toLocaleUpperCase()); // Output: “HELLO WORLD”

let str = “Hello WORLD”;
console.log(str.toLowerCase()); // Output: “hello world”

let str = “Hello World”;
console.log(str.toUpperCase()); // Output: “HELLO WORLD”

let date = new Date();
console.log(date); // Output: current date and time

let date = new Date();
console.log(date.getDate()); // Output: current day of the month

let date = new Date();
console.log(date.getDay()); // Output: current day of the week (0-6)

let date = new Date();
console.log(date.getFullYear()); // Output: current year (e.g. 2021)

let date = new Date();
console.log(date.getHours()); // Output: current hour (0-23)

let date = new Date();
console.log(date.getMilliseconds()); // Output: current millisecond (0-
999)

let date = new Date();
console.log(date.getMinutes()); // Output: current minute (0-59)

let date = new Date();
console.log(date.getMonth()); // Output: current month (0-11)

let date = new Date();
console.log(date.getSeconds()); // Output: current second (0-59)

let x = 10;
let y = 20;
let result = eval(‘x + y’);
console.log(result); // Output: 30

let angle = Math.PI / 4;
console.log(Math.sin(angle)); // Output: 0.7071067811865476
console.log(Math.cos(angle)); // Output: 0.7071067811865475
console.log(Math.tan(angle)); // Output: 0.9999999999999999

console.log(Math.abs(-10)); // Output: 10
console.log(Math.ceil(1.5)); // Output: 2
console.log(Math.floor(1.5)); // Output: 1
console.log(Math.log(10)); // Output: 2.302585092994046
console.log(Math.max(1, 2, 3)); // Output: 3
console.log(Math.min(1, 2, 3)); // Output: 1
console.log(Math.pow(2, 3)); // Output: 8
console.log(Math.random()); // Output: a random number between 0
and 1
console.log(Math.round(1.5)); // Output: 2
console.log(Math.sin(Math.PI / 2)); // Output: 1
console.log(Math.sqrt(25)); // Output: 5