| JavaScript賦值運算子 | 敘述 | 範例 |
|---|---|---|
| ＝ | x = y | x = y |
| +＝ | x += y | x = x + y |
| -＝ | x -＝ y | x = x - y |
| *＝ | x *＝ y | x = x * y |
| /＝ | x /= y | x = x / y |
| %＝ | x %= y | x = x % y |
| 運算子 | 敘述 | 範例 |
|---|---|---|
| + | 加號 | 1 + 1 = 2 |
| - | 減號 | 2 - 1 = 1 |
| * | 乘號 | 2 * 3 = 6 |
| / | 除號 | 10 / 2 = 5 |
| -- | 減去 | var a = 10; a--; Now a =9 |
| % | 餘數 | 20 % 3 = 2 |
| ++ | 遞增 | var a = 10; a++; Now a =10 |
| -- | 遞減 | var a = 10; a--; Now a =9 |
var name = 'Márquez';
var text = "His name is Marc Márquez";
你可以在引號中，再加入引號。如單引號中加入雙引號、雙引號中放置單引號。只要兩種引號不要一樣就好。var text = "His name is 'Marc Márquez'";
var text = 'and his opponent's name is "Valentino Rossi"';
承上例，除了使用不同樣式的引號外，我們還可以使用反斜杠（\），如下所示：var text = "His name is \"Marc Márquez\"";
var text = 'and his opponent's name is \'Valentino Rossi\';
var x = 777;在上述例子中，數值 777 被指定給變數 x。
var x = 100; document.write(X);
<html>
<head>
<script>
</script>
</head>
<body>
</body>
</html>
<html>
<head>
<script src="demo.js"> </script>
</head>
<body>
</body>
</html>
至於外部現成的 .js 檔，檔中文字就不能包含<script>...</script>標籤了。承上例，這個外部的 .js 檔「demo.js」內容如下：alert("Welcome to my page!");
則執行結果如下所示：
<script>
/* 這個code
會製造出一個
上面寫著
「Welcome to my page!」
的訊息對話框 */
alert("Welcome to my page!");
</script>
x = "There are %d types of people." % 10 binary = "binary" do_not = "don't" y = "Those who know %s and those who %s." % (binary, do_not) print x print y print "I said: %r." % x print "I also said: '%s'." % y hilarious = False joke_evaluation = "Isn't that joke so funny?! %r" print joke_evaluation % hilarious w = "This is the left side of..." e = "a string with a right side." print w + e如果上面的操作都沒問題，你將會看到下面的結果：
There are 10 types of people. Those who know binary and those who don't. I said: 'There are 10 types of people.'. I also said: 'Those who know binary and those who don't.'. Isn't that joke so funny?! False This is the left side of...a string with a right side.
>>>print dir(str)
執行結果如下：['__add__', '__class__', '__contains__', '__delattr__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__getnewargs__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__iter__', '__le__', '__len__', '__lt__', '__mod__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__rmod__', '__rmul__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', 'capitalize', 'casefold', 'center', 'count', 'encode', 'endswith', 'expandtabs', 'find', 'format', 'format_map', 'index', 'isalnum', 'isalpha', 'isascii', 'isdecimal', 'isdigit', 'isidentifier', 'islower', 'isnumeric', 'isprintable', 'isspace', 'istitle', 'isupper', 'join', 'ljust', 'lower', 'lstrip', 'maketrans', 'partition', 'replace', 'rfind', 'rindex', 'rjust', 'rpartition', 'rsplit', 'rstrip', 'split', 'splitlines', 'startswith', 'strip', 'swapcase', 'title', 'translate', 'upper', 'zfill']如果 dir() 的括弧內不帶任何參數物件，執行結果則會最大限度地顯示出當前範圍內的變數、方法和屬性列表。
['__annotations__', '__builtins__', '__doc__', '__loader__', '__name__', '__package__', '__spec__']
>>>help(‘dir’)
執行結果如下：Help on built-in function dir in module builtins:
dir(…)
dir([object]) -> list of strings
If called without an argument, return the names in the current scope.
Else, return an alphabetized list of names comprising (some of) the attributes
of the given object, and of attributes reachable from it.
If the object supplies a method named __dir__, it will be used; otherwise
the default dir() logic is used and returns:
for a module object: the module’s attributes.
for a class object: its attributes, and recursively the attributes
of its bases.
for any other object: its attributes, its class’s attributes, and
recursively the attributes of its class’s base classes.
while True:
print("選項:")
print("輸入 '+' 讓兩個數值互加")
print("輸入 '-' 讓兩個數值互減")
print("輸入 '*' 讓兩個數值互乘")
print("輸入 '/' 讓兩個數值互除")
print("輸入 'exit' 來結束程式")
user_input = input(": ")
if user_input == "exit":
break
elif user_input == "+":
...
elif user_input == "-":
...
elif user_input == "*":
...
elif user_input == "/":
...
else:
print("不知道你在輸入什麼")
上述程式還沒寫完，只完成了起始畫面與結構。接下來我們針對每個小部分來寫 Python 程式碼：elif user_input == "+":
num1 = float(input("請輸入數字:"))
num2 = float(input("請輸入另一個數字:"))
現在，當用戶輸入「+」後，程式就會提示輸入兩個數字。以上我們使用 float()函數，來將用戶輸入的數字強制轉變成浮點數。但是若用戶輸入的不是數字，程式就會 GG。elif user_input == "+":
num1 = float(input("請輸入數字:"))
num2 = float(input("請輸入另一個數字:"))
result = str(num1 + num2)
print("答案是 " + result)
以此類推，減法的部分為:elif user_input == "-":
num1 = float(input("請輸入數字:"))
num2 = float(input("請輸入另一個數字:"))
result = str(num1 - num2)
print("答案是 " + result)
以此類推，乘法的部分為:elif user_input == "*":
num1 = float(input("請輸入數字:"))
num2 = float(input("請輸入另一個數字:"))
result = str(num1 * num2)
print("答案是 " + result)
以此類推，除法的部分為:elif user_input == "/":
num1 = float(input("請輸入數字:"))
num2 = float(input("請輸入另一個數字:"))
result = str(num1 / num2)
print("答案是 " + result)
程式寫好，執行成果如下:
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