AngularJS – 跟著Google玩網頁！
今天馬老師要與大家分享的是一個前端開發的函式庫AngularJS，前面的文章中都有提到，因為近年來行動裝置的普及讓Javascript大為活躍，不過傳統的Javascript在相容性上、操作上都非常的不方便，所以才有了許許多多Javascript的函式庫與框架的誕生，例如：jQuery、KnockoutJS、GSAP、PaperJS…等，每個Javascript的函式庫和框架的大小、作用和目的都不盡相同，有的是為了特效；有的則是為了方便操作，那今天為何要跟大家分享AngularJS呢？因為…它是名牌！
為何說AngularJS是名牌呢？因為目前他是由Google來負責維護。初始版本是在2009年誕生的，比jQuery晚了三年，言下之意就會比jQuery好嗎？當然也不能這麼說，jQuery在目前還是一個非常火燙的前端開發函式庫，應該要說他們兩個在使用的架構和目的上會有所不同，這篇文章也來比較一下同樣的案例，在兩種語法上面撰寫的不同。
不過首先我們要知道基本的AngularJS開發方式，今天的案例我們利用JS Bin的線上開發網頁來說明，大家也可以到這個平台上來試著玩看看！如果需要利用AngularJS開發自己的網頁，也可以到AngularJS的官方網頁把JS下載到資料夾之後引用到網頁裡。
1. 首先點選Add library後選擇AngularJS Stable，這樣該平台就會加入AngularJS的函式庫進入頁面。
2. 在標籤中，加入ng-app的屬性，讓整份文件都可以使用AngularJS。
3. 接下來就可以在左手邊body標籤內開始輸入一些程式碼來測試，AngularJS在輸出方面有個基本的結構式「{{ }}」，大家輸入以下的程式碼來測試看看結果：
<!DOCTYPE html>
<html ng-app>
<head>
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.3.2/angular.min.js"></script>
<meta charset="utf-8">
<title>JS Bin</title>
</head>
<body>
<p>{{ '馬老師雲端研究室' }}</p>
<p>35+62={{ 35+62 }}</p>
<p>NT{{ 62000 | currency }}</p>
</body>
</html>
可以看到輸出的結果應該是：（在JS Bin上面看AngularJS輸出結果）
馬老師雲端研究室 35+62=97 NT$62,000.00
同樣的如果我們要利用jQuery來完成這樣的頁面，程式碼就會變成：（在JS Bin上面看jQuery輸出結果）
<!DOCTYPE html>
<html>
<head>
<script src="https://code.jquery.com/jquery-1.11.1.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/numeral.js/1.4.5/numeral.min.js"></script>
<meta charset="utf-8">
<title>JS Bin</title>
</head>
<body>
<p></p>
<p></p>
<p></p>
</body>
</html>
<script>
$("p:eq(0)").text('馬老師雲端研究室')
$("p:eq(1)").text('35+62=' + (35 + 62))
$("p:eq(2)").text('NT' + (numeral(62000).format('$ 0,0.00')))
</script>
請注意，為了要完成第三項貨幣型式的呈現，我們還必須去引用這個網站的jQuery Plugin才有辦法比較輕鬆的實現。從上面的案例可以看的出來jQuery是由HTML DOM來抓到對象，再針對對象做操作，而AngularJS不管顯示的效果為何，就是在需要有程式運算的地方出現，所以AngularJS也被稱為符合MVC結構的Javascript函式庫（MVC是一種寫程式的結構，全名是Model View Controller，大家可以上網Google就可以查到很多與MVC相關的資料），但如果你有進入官網，可以看到官網上他的標題是「AngularJS – Superheroic JavaScript MVW Framework」，翻譯成中文大概是「AngularJS是一個符合MV…Whatever什麼什麼隨便啦！的超級函式庫」，可以看出Google的惡搞功夫。
再來示範第二個案例，本案例利用購物行為來製作相關的頁面讓大家參考，程式碼如下：
<!DOCTYPE html>
<html ng-app>
<head>
<script src="http://ajax.googleapis.com/ajax/libs/angularjs/1.3.2/angular.min.js"></script>
<meta charset="utf-8">
<title>JS Bin</title>
</head>
<body ng-init="stock=120;price=325;quantity=1;total=0">
<p>馬老師雲端研究室 滑鼠墊</p>
<p>剩餘：<span ng-model="stock">{{ stock-quantity }}</span>個</p>
<p>單價：<span ng-model="price">{{ price | currency:"NT$":0 }}</span>元</p>
<p>數量：<input type="number" min="0" max="{{ stock }}" ng-model="quantity"></p>
<p>總金額：<span ng-model="total">{{ price*quantity | currency:"NT$":0 }}</span></p>
</body>
</html>
輸出結果：（在JS Bin上面看AngularJS輸出結果）
在這個案例裡面有四個項目，分別是商品剩餘數量、單價、數量、總金額，使用者唯一可以改變的只有數量，但頁面中會自動運算剩餘數量和總金額，其中在語法body標籤中，加上了ng-init屬性，代表設定這幾個項目的預設值，stock（剩餘數量）120個、price（單價）325元、quantity（數量）1個，total（總金額）325元。接下來在span內的ng-model就是去綁定該定義項目，{{ }}則是顯示該項目或運算結果，另外貨幣格式的部分，也是用了一些設定讓貨幣在這個案例裡面顯示得更為接近台幣格式，另外還是用HTML5 input標籤的min和max來限制欄位內的值。 而這個案例如果轉換為jQuery的寫法，大概會是下面這樣子：（在JS Bin上面看jQuery輸出結果）
<!DOCTYPE html>
<html>
<head>
<script src="http://code.jquery.com/jquery-1.11.1.min.js"></script>
<script src="http://cdnjs.cloudflare.com/ajax/libs/numeral.js/1.4.5/numeral.min.js"></script>
<meta charset="utf-8">
<title>JS Bin</title>
</head>
<body>
<p>馬老師雲端研究室 滑鼠墊</p>
<p>剩餘：<span id="stock"></span>個</p>
<p>單價：<span id="price"></span>元</p>
<p>數量：<input type="number" min="0" ng-model="quantity" id="quantity"></p>
<p>總金額：<span id="total"></span>元</p>
</body>
</html>
<script>
var stock = 120;
var price = 325;
var quantity = 1;
var total = 325;
$("#stock").text(stock) $("#price").text('NT' + (numeral(price).format('$ 0,0'))) $("#quantity").val(quantity).attr(
"max", stock) $("#total").text('NT' + (numeral(total).format('$ 0,0'))) $("#quantity").change(function () {
quantity = $(this).val() newstock = stock - $(this).val() total = price * $(this).val() $("#stock").text(
newstock) $("#price").text('NT' + (numeral(price).format('$ 0,0'))) $("#total").text('NT' + (
numeral(total).format('$ 0,0')))
})
</script>
後記：以上兩個案例示範的是jQuery和AngularJS在撰寫頁面的不同，不過因為這篇文章原本就是要以AngularJS為主，所以挑的案例當然會是AngularJS比較佔優勢的內容，還是跟我常說的一樣，做不同的東西就要用不同的工具，用錯了工具不是做不到，但可能是會事倍功半的！另外文章中的程式碼，都是嵌入遠端的JS檔，所以也可以把整個程式碼複製到你熟悉的網頁開發軟體內，一樣會看到同樣的結果喔！
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