By GokiSoft.com| 20:21 24/11/2021|
Học JS

[Share Code] Tìm hiểu kiến thức căn bản trong Javascript (biến, toán tử, mệnh đề điều kiên, vòng lặp) - Lập trình Javascript

#function.html


<!DOCTYPE html>
<html>
<head>
	<meta charset="utf-8">
	<meta name="viewport" content="width=device-width, initial-scale=1">
	<title>Function javascript tutorial</title>
</head>
<body>
	<h1 style="text-align: center;">Tim hieu function trong javascript</h1>

<script type="text/javascript">
	function showMenu() {
		console.log('1. Nhap thong tin sinh vien')
		console.log('2. Hien thi thong tin sinh vien')
		console.log('3. Tim kiem')
		console.log('Chon: ')
	}

	showMenu()

	//Cach code -> ko co kha nang tai su dung code
	var total = 0
	for (var i = 0; i <= 10; i++) {
		total += i
	}
	console.log(total)

	//Cach code -> ko co kha nang tai su dung code
	var total = 0
	for (var i = 0; i <= 100; i++) {
		total += i
	}
	console.log(total)

	function tinhtong(n) {
		var total = 0
		for (var i = 0; i <= n; i++) {
			total += i
		}
		console.log(total)
	}

	tinhtong(5)
	tinhtong(10)
	tinhtong(100)

	function tinhtong2(n, m) {
		var total = 0
		for (var i = n; i <= m; i++) {
			total += i
		}
		// console.log(total)
		return total
	}

	t1 = tinhtong2(5, 10)
	t2 = tinhtong2(7, 11)
	console.log(`t1 = ${t1}, t2 = ${t2}`)

	function changeValue(y) {
		y += 2
		console.log('y = ' + y)
	}

	x = 6//string, int, boolean, float, double, char -> kieu du lieu nguyen thuy
	changeValue(x)
	console.log('x = ' + x)
</script>
</body>
</html>


#index.html


<!DOCTYPE html>
<html>
<head>
	<meta charset="utf-8">
	<meta name="viewport" content="width=device-width, initial-scale=1">
	<title>Javascript tutorial</title>
</head>
<body>
	<h1 style="text-align: center;">Tìm hiểu kiến thức javascript căn bản</h1>
	<!-- Comment HTML/CSS -->
<script type="text/javascript">
	//noi cac trien khai code javascript
	//Phan: Tim hieu khai bao bien
	var s = 12;//s: kieu du lieu la int
	var t = 'Xin Chao' //t: kieu du lieu la string/text

	s = 'Sinh vien Aptech 54 Le Thanh Nghi' //Luc nay -> se hieu s: kieu du lieu la String/text
	document.write('gia tri s = <strong style="color: red">' + s + '</strong>')
	document.write('<br/>' + t)
	document.write(`<br/>s = ${s}, t = ${t}`);

	str = 'Xin Chao ABC'
	document.write(`<br/>str = ${str}`)

	console.log(str)
	console.log('Test...')
	//Chuan coding convention trong dat ten bien:
	//first letter (ky tu dau tien): a-zA-Z_
	//next letter (cac ky tu tiep theo): a-zA-Z_0-9
	//Ten bien ko duoc trung vs keyword
	/**
	 * Comment khoi code
	 */
	//alert('Vui long kiem tra thong tin tai khoan cua ban')
	// var option = confirm('Ban chac chan muon chia se thong tin tai khoan voi chung toi ko???')
	// console.log(option)
	// var fullname = prompt('Nhap ho & ten')
	// console.log(fullname)
	var x = 5
	var y = 7
	var tong = x + y
	console.log('r = ' + tong)
	r = x - y
	console.log('r = ' + r)
	r = x * y
	console.log('r = ' + r)

	x = '5' //string
	y = 7 //int
	tong = x + y //uu tien -> noi chuoi (string/text) -> 57
	console.log('r = ' + tong)
	r = x - y //phep tinh '-' => ton tai trong toan hoc -> int -> -2
	console.log('r = ' + r)
	r = x * y //phep tinh '*' => ton tai trong toan hoc -> int -> 35
	console.log('r = ' + r)

	//Lap trinh javascript -> loi khi su dung phep tinh + (nham lan giua + toan hoc hoac cong chuoi (string))
	//khi lap trinh -> bien la string hay int -> kho xac dinh -> su dung phep + -> chuong trinh rat de xay ra ket qua ko nhu mong muon.

	//Khi code -> su dung phep tinh + -> danh cho toan hoc
	x = parseInt(x) //x -> ve kieu du lieu int (string, int -> int)
	y = parseInt(y)
	r = x + y
	console.log('r = ' + r)
	// x = prompt('Nhap x:', 10)
	/**
	x = prompt('Nhap x:')
	y = prompt('Nhap y:')
	r = x + y
	alert(r)
	x = parseInt(x)
	y = parseInt(y)
	r = x + y
	alert(r)
	r = `${x}${y}`
	alert(r)
	r = '' + x + y;
	alert(r)
	*/
	// s = 'var x=5;var y=7;var k = x + y;alert(k)';//string
	// console.log(s)
	// eval(s)

	//ky thuat hack -> hacker su dung
	// s = 'dmFyIHg9NTt2YXIgeT03O3ZhciBrID0geCArIHk7YWxlcnQoayk='
	// s = atob(s)
	// eval(s)

	k = 6
	s = (k==5)?'Xin Chao':'Goodbye'
	console.log(s)

	var t = k++
	var m = ++k
	//8|6|8
	console.log(`k=${k}, t=${t}, m=${m}`)
	//k = 8, m = 8
	var j = k++ + ++k - --m + 1
	//j = 8(k=9) + (k=10)10 - (m=7)7 + 1 = 12
	console.log(`k=${k}, j=${j}, m=${m}`)

	var pattern = /[+0-9. ]{9,16}/
	var phone = '0967025$$$996'
	var check = pattern.exec(phone)

	console.log(check)
</script>
</body>
</html>


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