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# Ninja code

## Brevity is the soul of wit

極簡的極致，相看兩不厭，只有一行碼。

```coffeescript
// taken from a well-known javascript library
i = i ? i < 0 ? Math.max(0, len + i) : i : 0;
```

## One-letter variables

一個字母的變數，沒人知道代表的意思。

## Use abbreviations

只有通靈王能知道縮寫代表的意思，盡情使用吧！

* `list` → `lst`.
* `userAgent` → `ua`.
* `browser` → `brsr`.
* …etc

## Soar high. Be abstract.

* 最適合變數的名稱 `data` `value` 乍看之下很正常，實際上沒有任何意義。
* 用資料類型命名，`str` `num`
* 找不到更多變數，後面加數字 `item2` `data1`

## Smart synonyms

對於同樣的事情用不同前綴，不同的兩件事情用相同的前綴。

* `displayMessage` vs `showName` (顯示在螢幕上)
* `printPage` (印出來) vs `printText` (顯示在螢幕上)

## Reuse names

重複使用已存在的變數，更進階的用法式在函式中間重新使用。

```javascript
function ninjaFunction(elem) {
  // 20 lines of code working with elem

  elem = clone(elem);

  // 20 more lines, now working with the clone of the elem!
}
```

## Underscores for fun

在變數前使用 `_` `__` 而且沒人知道他們代表的意思。

1. 降低可讀性
2. 花很長時間弄清楚下畫線的意思

## Show your love

寫的一堆沒用的形容詞，`superElement`  `megaFrame` `niceItem` 。

## Overlap outer variables

```javascript
let user = authenticateUser();

function render() {
  let user = anotherValue();
  ...
  ...many lines...
  ...
  ... // <-- a programmer wants to work with user here and...
  ...
}
```

## Side-effects everywhere!

`isReady()`  `checkPermission()` 假設只會執行內部運算不會影響函式外的變數，結果使用時改變了外面的變數或返回的值不是布林值，你同事的表情一臉矇逼爽！

## Powerful functions!

函數不只執行一個動作時，你的同事用不著這個函式，他就不會來煩你了。


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