vue.js 學習手冊 框架的選擇與導入
這篇文章是vue.js學習手冊的第一篇文章，也是我認為最難寫的一篇文章，就像vue.js提到的他是一個“漸進式”框架，在這篇文章也想要跟各位分享選擇框架的一些原則，讓大家可以“漸進式”的了解為什麼我們在網頁開發時需要選擇一個框架來幫助我們，在選擇框架之前我們要先弄清楚，框架究竟可以幫助我們在網頁開發上的哪些部分，如果這些部分跟你要開發的項目並不媒合，那奉勸你別把單純的事情搞複雜了，而且你可能會開始討厭學習框架，但若反之，你一定會愛上框架，甚至覺得他讓你事半功倍。
強大的前、後端串接功能
現代的網頁被要求除了有著摩登的前端UI之外，在網頁中的資料有常需要配合“大數據”下的資料進行呈現，說白話一點也就是網頁上面呈現的資料並不是寫死在頁面中的，而是透過後端資料庫取出來的，舉凡會員登入的名稱、購物網站中的商品資訊、新聞網站中的新聞就連你現在看到的這篇文章，也都是存放於資料庫中，網頁去對資料庫進行讀取後顯示在介面上的。
當然除了對資料庫進行讀取之外，網頁也會對資料庫進行儲存的動作，舉凡會員資料修改、商品訂單建立、網站偏好設定…等等，而框架在這方面有許多很好的方法，讓我們可以更周全快速的處理這方面的動作，節省許多開發的時間與減少Bug上的產生。
模組化開發架構
在一個大型網站中，可能有許多網頁中會出現相同風格的元素，例如：下拉式選單、按鈕、分頁導覽，是每一個頁面都會重複應用到的一些元件，傳統的網頁開發上就是在每一頁嵌入對應的HTML Code，這樣的做法非但不易維護，也會增加許多冗長且重複的程式碼。
模組化開發可以如上圖所示，將頁面中需重用的元素拉出來設計成一個Component，在不同頁面可以透過引入的方式置入該Component，而Component的維護可以統一在該Component中進行，可以減少大量維護上的時間。
透過 Virtual DOM 來提升頁面效能
現代的網頁前端框架為了提升頁面操作的效能都提供了Virtual DOM，在Vue.js 2.0中也引入Virtual DOM，比Vue.js 1.0的初始渲染速度提升了2~4倍，並大大降低了內存消耗，至於為何Virtual DOM能提昇網頁的效能，大家就必須了解我們透過Javascirpt更新實體DOM時會產生的效能問題開始了解。
實體DOM更新的效能測試
這邊製作一個簡單的範例對實體DOM和虛擬DOM的效能進行說明：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title></title>
</head>
<body>
<div class="wrapper">
<div class="container">
<div class="itemList">
<ul id="itemList__ul">
<li id="liID">Item 1</li>
</ul>
</div>
</div>
<button onClick="insertItems()">Go</button>
</div>
</body>
</html>
<script>
var itemData = "";
function insertItems() {
for (var i = 1; i <= 100000; i++) {
itemData = "Item " + i
document.getElementById("liID").innerHTML = itemData;
}
}
</script>
在HTML DOM的操作上，只要頁面元素有變更，就可能會觸發Reflow或Repaint這樣的動作，瀏覽器也會耗費相當多的資源在進行這些動作，以上述的例子來看，當我們按下頁面上的按鈕之後，就會透過迴圈去改變li的內容，這樣將會觸發多次的瀏覽器動作。
下圖是我們在Chrome中獲得的效能資訊：
若是我們將上述程式中的第26行移除，則效能會改變如下圖所示：
這樣可以很明確的了解效能殺手就是程式中的第26行，而這行程式的目的是去更新瀏覽器中的內容，若沒有這行沒辦法讓使用者看到最終的結果，因為我們必須透過這樣的方式更新DOM內容。
虛擬DOM的效能測試
同樣頁面的效果，我們在Vue裡面的作法如下：
<!DOCTYPE html>
<html lang="zh">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title></title>
<script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
</head>
<body>
<div id="app">
<ul>
<li v-for="item in items">{{ item.message }}</li>
</ul>
<button @click="insertItems">Go</button>
</div>
</body>
</html>
<script>
var vueData = {
items: [
{ message: 'Item 1' }
]
}
var app = new Vue({
el: '#app',
data: vueData,
methods: {
insertItems: function(){
for(var i = 1; i <= 100000; i ++){
vueData.items[0].message = "Item " + i;
}
}
}
})
</script>
同樣的結果在Vue會在Javascript和瀏覽器中加入一層Virturl DOM，待Virturl DOM更新完畢之後，在寫入瀏覽器中。
透過這樣的方法，使用這得到的一樣的效果，但大大提高了使用者端瀏覽器的效能，可以從下圖觀察的出來！
在Virtual DOM的架構中，會把程式的動作動作集中在Virtual DOM中運算，當確定整個頁面結構之後，再一次性地將結果繪製到頁面中，可以想像成原本的DOM操作就是在每一次在CPU運算之後，直接把結果寫到硬碟當中，而Virtual DOM就是在CPU與硬碟間加入了記憶體層，CPU運算後先將結果儲存在記憶體中，最後再將記憶體的資料一次性的寫入硬碟。
PS：記憶體的運算速度超過硬碟很多倍。
結論
綜合上述所說，網頁專案中採用前端框架，有著減少開發時間、易於維護、增加頁面效能…等優點，但若你的專案並不會大量與後端串接、製作上元件重複使用的機會不高、在頁面中也不太會對DOM進行Reflow與Repaint，可能是一個活動網頁、公司形象網頁…等，也許就沒有必要去選用一個前端框架，簡言之工具用在正確的地方，才能顯現出它的價值，當然目前符合使用框架的專案也一定非常多，也就是這樣的原因，才會造成前端框架的流行。
http://clssansordonnance.icu/# pharmacie en ligne france fiable
cheap skips hire near me
Look of the Week: Forget the naked dress, Kendall Jenner makes the case for underwear as outerwear
kraken darknet
On Monday, Kendall Jenner stepped out onto the L’Oreal Paris womenswear runway in a scarlet red Mugler gown that might have looked familiar to anyone with a sharp memory of 1999.
The front of the dress was slashed open across Jenner’s right shoulder, exposing a matching denier bra. The peekaboo moment conjured up memories of another example of fashionable flashing: Lil’ Kim’s purple embellished jumpsuit at the VMAs 26 years earlier. On the red carpet, Kim’s left breast was almost entirely revealed by an asymmetrical cut — a mirror image of Jenner’s neckline — save for a matching purple nipple pasty.
Jenner’s Mugler moment was just the latest example of a resurging tendency for underwear as outerwear. At the Nensi Dojaka runway show in London earlier this month, boxy blazers were shrugged over strappy bras while paneled bustiers in sheer fabric were paired with capri trousers and reimagined as going out tops. Brasseries were even left exposed to the elements at Erdem — a departure for a house beloved by both British acting royalty (Kristen Scott Thomas) and actual royalty (the Duchess of Cambridge). Dolce & Gabbana got the memo, too, showing satin corsets, garter belts and Madonna-esque cone bras at Milan Fashion Week on Saturday. Florence Pugh even wore one of the label’s risque designs in her first British Vogue cover last week — the circle neckline of her puff-shouldered black dress scooping just above the belly button, acting as a full-frontal frame for her bra.
But the trend extends beyond just the runways. During the first performance of her “Short n’ Sweet” tour on Monday, singer Sabrina Carpenter took to the stage in a custom Victoria’s Secret bodysuit and stockings. Hand-adorned with over 150,000 crystals, the strapless pink lace-trimmed leotard took over 140 hours to make. On Monday,YouTube star and singer Jojo Siwa inverted the fad by donning a codpiece for a headline-grabbing cover shoot with LadyGunn magazine. The 15th century undergarment was bedazzled with flesh-colored gemstones.
Официальная покупка диплома вуза с сокращенной программой обучения в Москве
jogibaba.com/blogs/377/Ваш-диплом-без-лишних-проблем
Стоимость дипломов высшего и среднего образования и процесс их получения
hire skip glasgow
Профессиональный сервисный центр по ремонту бытовой техники с выездом на дом.
Мы предлагаем:сервисные центры по ремонту техники в уфе
Наши мастера оперативно устранят неисправности вашего устройства в сервисе или с выездом на дом!
https://clssansordonnance.icu/# Pharmacie Internationale en ligne
Быстрое обучение и получение диплома магистра – возможно ли это?
shoptema.ru/forum/topic/33052
Купить диплом старого образца, можно ли это сделать по быстрой схеме?
Стоимость дипломов высшего и среднего образования и процесс их получения
Профессиональный сервисный центр по ремонту бытовой техники с выездом на дом.
Мы предлагаем:ремонт бытовой техники в уфе
Наши мастера оперативно устранят неисправности вашего устройства в сервисе или с выездом на дом!
pharmacies en ligne certifiГ©es Pharmacie sans ordonnance trouver un mГ©dicament en pharmacie
Sildenafil teva 100 mg sans ordonnance viagra sans ordonnance Viagra vente libre pays
Полезные советы по безопасной покупке диплома о высшем образовании
bbs.ou-lei.com/home.php?mod=space&uid=396045
Полезные советы по безопасной покупке диплома о высшем образовании
Узнайте стоимость диплома высшего и среднего образования и процесс получения
Вопросы и ответы: можно ли быстро купить диплом старого образца?
eurosan-spa.ru/otoplenie/pochemu-nuzhen-diplom-specialista-i-chto-nuzhno-dlya-ego-polucheniya
Профессиональный сервисный центр по ремонту бытовой техники с выездом на дом.
Мы предлагаем: сервисные центры в москве
Наши мастера оперативно устранят неисправности вашего устройства в сервисе или с выездом на дом!
Профессиональный сервисный центр по ремонту плоттеров в Москве.
Мы предлагаем: сервис по ремонту плоттеров
Наши мастера оперативно устранят неисправности вашего устройства в сервисе или с выездом на дом!
Сервисный центр предлагает адреса ремонта квадрокоптеров сервис ремонта квадрокоптеров
pharmacie en ligne france livraison internationale: п»їpharmacie en ligne france – Pharmacie Internationale en ligne
Реально ли приобрести диплом стоматолога? Основные этапы
Big Wins in Sweet Bonanza – Success Stories Hear real success stories from players who hit big in Sweet Bonanza. Learn how they triggered huge multipliers and free spins to take home massive rewards!
slot bonanza
Как оказалось, купить диплом кандидата наук не так уж и сложно
mini skips for hire
mcguire skip hire glasgow
Cheapest skip hire near me
Сервисный центр предлагает починить бесперебойника legrand качественый ремонт бесперебойников legrand
Look of the Week: Forget the naked dress, Kendall Jenner makes the case for underwear as outerwear
kra10 cc
On Monday, Kendall Jenner stepped out onto the L’Oreal Paris womenswear runway in a scarlet red Mugler gown that might have looked familiar to anyone with a sharp memory of 1999.
The front of the dress was slashed open across Jenner’s right shoulder, exposing a matching denier bra. The peekaboo moment conjured up memories of another example of fashionable flashing: Lil’ Kim’s purple embellished jumpsuit at the VMAs 26 years earlier. On the red carpet, Kim’s left breast was almost entirely revealed by an asymmetrical cut — a mirror image of Jenner’s neckline — save for a matching purple nipple pasty.
Jenner’s Mugler moment was just the latest example of a resurging tendency for underwear as outerwear. At the Nensi Dojaka runway show in London earlier this month, boxy blazers were shrugged over strappy bras while paneled bustiers in sheer fabric were paired with capri trousers and reimagined as going out tops. Brasseries were even left exposed to the elements at Erdem — a departure for a house beloved by both British acting royalty (Kristen Scott Thomas) and actual royalty (the Duchess of Cambridge). Dolce & Gabbana got the memo, too, showing satin corsets, garter belts and Madonna-esque cone bras at Milan Fashion Week on Saturday. Florence Pugh even wore one of the label’s risque designs in her first British Vogue cover last week — the circle neckline of her puff-shouldered black dress scooping just above the belly button, acting as a full-frontal frame for her bra.
But the trend extends beyond just the runways. During the first performance of her “Short n’ Sweet” tour on Monday, singer Sabrina Carpenter took to the stage in a custom Victoria’s Secret bodysuit and stockings. Hand-adorned with over 150,000 crystals, the strapless pink lace-trimmed leotard took over 140 hours to make. On Monday,YouTube star and singer Jojo Siwa inverted the fad by donning a codpiece for a headline-grabbing cover shoot with LadyGunn magazine. The 15th century undergarment was bedazzled with flesh-colored gemstones.