jsBasics_Practice-JS Tutorial-php.cn

jsBasics_Practice

Linda Hamilton

Release： 2024-11-23 06:47:15

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jsBasics_Practice

Basics

What are the types of these variables listed below ? Verify this with typeof and output the result to the console:

let str1 = 'Laurence';
console.log(typeof (str1));   //string
let str2 = "Svekis";
console.log(typeof (str2));  //string
let val1 = undefined;
console.log(typeof (val1));  //undefined
let val2 = null;
console.log(typeof (val2));  //object
let myNum = 1000;
console.log(typeof (myNum)); //number

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What data type is the following variable?

const c = "5"; //string
const d = 91;  // number

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Which one is generally better, line 1 or line 2?

let empty1 = undefined; //line 1
let empty2 = null; //line 2

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What is the console output for the following?

let a1 = "Hello";
a1 = "world";
console.log(a1);  //world

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let a2 = "world";
let b2 = Hello ${a2}!;
console.log(b2);  // Helloworld

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What is the value..?

let a4 = 5;
let b4 = 70;
let c4 = "5";
b4++;
console.log(b4);  //71

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let result = 3 4 * 2 / 8; // 4, doesn't print anything as we didn't log the result.

let firstNum = 5;
let secondNum = 10;
firstNum++;
secondNum--;
let total = ++firstNum + secondNum;
console.log(total);  //16
let total2 = 500 + 100 / 5 + total--;
console.log(total2);  // 536

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const a = 5;
const b = 10;
console.log(a > 0 && b > 0);  // true
console.log(a == 5 && b == 4);  // false
console.log(true || false);  // true
console.log(a == 3 || b == 10);  // true
console.log(a == 3 || b == 7);  // false

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