タグ: programming

Javascript 数値か文字列か

index.html

<!DOCTYPE html>
<html lang="ja">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>My JavaScript</title>
</head>
<body>
  <script src="main.js"></script>
</body>
</html>

main.js

'use strict';

//console.log(50 + '20');

const n = prompt('Any number?');
console.log(Number(n) + 10);

Javascript 文字列の操作

index.html

<!DOCTYPE html>
<html lang="ja">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>My JavaScript</title>
</head>
<body>
  <script src="main.js"></script>
</body>
</html>

main.js

'use strict';

const fname = 'Taro';
const lname = 'Yamada';

//console.log('My name is ' + fname + ' ' + lname + ', call me ' + fname + '!');
console.log('My name is ${fname} ${lname}, call me $(fname)!');

Javascript 文字列

index.html

<!DOCTYPE html>
<html lang="ja">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>My JavaScript</title>
</head>
<body>
  <script src="main.js"></script>
</body>
</html>

main.js

'use strict';

// console.log('It is a pen.');
// console.log('It\'s a pen.');
// console.log("It's a pen.");
console.log("It's \na \npen.");

Javascript 変数に値を再代入

index.html

<!DOCTYPE html>
<html lang="ja">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>My JavaScript</title>
</head>
<body>
  <script src="main.js"></script>
</body>
</html>

main.js

'use strict';

/*
Javascriptにおける数値の表現
*/
// console.log(150 * 120 * 1.1);
// console.log(150 - 130 * 1.1);
// console.log(150 * 140 * 1.1);

//変数
let price;
//定数
const rate = 1.1;

price = 150;
console.log(price * 120 * rate);
console.log(price * 130 * rate);
console.log(price * 140 * rate);

price++;
console.log(price * 120 * rate);
console.log(price * 130 * rate);
console.log(price * 140 * rate);

Javascript 変数

index.html

'use strict';

/*
Javascriptにおける数値の表現
*/
// console.log(150 * 120 * 1.1);
// console.log(150 - 130 * 1.1);
// console.log(150 * 140 * 1.1);

//変数
let price;
//定数
const rate = 1.1;

price = 150;
console.log(price * 120 * rate);
console.log(price * 130 * rate);
console.log(price * 140 * rate);

price = 151;
console.log(price * 120 * rate);
console.log(price * 130 * rate);
console.log(price * 140 * rate);

main.js

'use strict';

/*
Javascriptにおける数値の表現
*/
// console.log(150 * 120 * 1.1);
// console.log(150 - 130 * 1.1);
// console.log(150 * 140 * 1.1);

//変数
let price;
//定数
const rate = 1.1;

price = 150;
console.log(price * 120 * rate);
console.log(price * 130 * rate);
console.log(price * 140 * rate);

price = 151;
console.log(price * 120 * rate);
console.log(price * 130 * rate);
console.log(price * 140 * rate);

Javascript 定数

index.html

<!DOCTYPE html>
<html lang="ja">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>My JavaScript</title>
</head>
<body>
  <script src="main.js"></script>
</body>
</html>

main.js

'use strict';

/*
Javascriptにおける数値の表現
*/
// console.log(150 * 120 * 1.1);
// console.log(150 - 130 * 1.1);
// console.log(150 * 140 * 1.1);

//定数
const price = 150;
const rate = 1.1;

console.log(price * 120 * rate);
console.log(price * 130 * rate);
console.log(price * 140 * rate);

Javascript 数値の演算

index.html

<!DOCTYPE html>
<html lang="ja">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>My JavaScript</title>
</head>
<body>
  <script src="main.js"></script>
</body>
</html>

main.js

'use strict';

/*
Javascriptにおける数値の表現
*/
console.log(10 + 3);
console.log(10 - 3);
console.log(10 * 3);
console.log(10 ** 3);
console.log(10 / 3);
console.log(10 % 3);

console.log(10 + 2 * 3);
console.log((10 + 2) * 3);

Javascript コメント

index.html

<!DOCTYPE html>
<html lang="ja">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>My JavaScript</title>
</head>
<body>
  <script src="main.js"></script>
</body>
</html>

main.js

'use strict';

/*
Javascriptにおける数値の表現
*/
console.log(100);
console.log(-10);
console.log(2.5);

//大きな数値、小さな数値の表現
console.log(1.2e4); //1.2かける10の４乗
console.log(1.2e-4);//1.2かける10の-４乗

Javascript 数値

index.html

<!DOCTYPE html>
<html lang="ja">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>My JavaScript</title>
</head>
<body>
  <script src="main.js"></script>
</body>
</html>

main.js

'use strict';

console.log(100);
console.log(-10);
console.log(2.5);

console.log(1.2e4);
console.log(1.2e-4);

Javascript Console.log

<!DOCTYPE html>
<html lang="ja">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>My JavaScript</title>
</head>
<body>
  <script src="main.js"></script>
</body>
</html>

index.html

'use strict';

console.log(100);

main.js