JavaScript-邏輯運算子

    AllenLi
    Coding

    JavaScript的運算子：
    在JavaScript中透過運算符號來賦予指定變數對應的數值。

    +----------+----------+-------------+
| Name     | Abridge  | Mean        |
+----------+----------+-------------+
| =        | 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   |
| **       | 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   |
| ^        | x ^= y   | x = x ^ y   |
| |        | x |= y   | x = x | y   |
+----------+----------+-------------+

    JavaScript的比較運算子：
    在JavaScript中遇到需要對數值進行運算、字串進行判斷時，
    可以運用比較運算來執行，同時需注意嚴謹的做法。

    +----------+-----------+--------+
| Operator | Usage     | Result |
+----------+-----------+--------+
| ==       | 0 == '0'  | True   |
|          | 0 == ''   | True   |
+----------+-----------+--------+
| ===      | 0 === '0' | False  |*
|          | 0 ===  '' | False  |*
+----------+-----------+--------+
| !=       | 0 != '0'  | False  |
|          | 0 !=  ''  | False  |
+----------+-----------+--------+
| !==      | 0 !== '0' | True   |*
|          | 0 !==  '' | True   |*
+----------+-----------+--------+
| >        | 1 > 0     | True   |
|          | 1 > 1     | False  |
|          | 0 > 1     | False  |
+----------+-----------+--------+
| >=       | 1 >= 0    | True   |
|          | 1 >= 1    | True  |
|          | 0 >= 1    | False  |
+----------+-----------+--------+
| <        | 1 < 0     | False  |
|          | 1 < 1     | False  |
|          | 0 > 1     | True   |
+----------+-----------+--------+
| <=       | 1 <= 0    | False  |
|          | 1 <= 1    | True   |
|          | 0 <= 1    | True   |
+----------+-----------+--------+

    JavaScript的邏輯運算子：
    在JavaScript中碰到需要判斷對與錯時，可以使用布林運算子來進行判斷。

    +----------+----------------+--------+
| Operator | Usage          | Result |
+----------+----------------+--------+
| &&       | True && True   | True   |
|          | True && False  | False  |
|          | False && False | True   |
+----------+----------------+--------+
| ||       | True || True   | True   |
|          | True || False  | True   |
|          | False || False | False  |
+----------+----------------+--------+
| !        | !True          | False  |*
|          | !False         | True   |*
+----------+----------------+--------+

    JavaScript的解構賦值：

    var num = ['I', 'II', 'III'];

// 不使用解構
var I   = num[0];
var II  = num[1];
var III = num[2];

// 使用解構
var [I, II, III] = num;

    JavaScript的三元運算子：

    function getFee(isMember) {
  return (isMember ? '$2.00' : '$10.00');
}

console.log(getFee(true));
// expected output: "$2.00"

console.log(getFee(false));
// expected output: "$10.00"

console.log(getFee(null));
// expected output: "$10.00"

    參考資料來源：JavaScript mdn

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