【Seajs源码分析】3. 工具方法2

util-request.js 动态加载模块

/**
* util-request.js - The utilities for requesting script and style files
* ref: tests/research/load-js-css/test.html
*/

var head = doc.head || doc.getElementsByTagName("head")[0] || doc.documentElement
var baseElement = head.getElementsByTagName("base")[0]

var IS_CSS_RE = /\.css(?:\?|$)/i
var currentlyAddingScript
var interactiveScript

// `onload` event is not supported in WebKit < 535.23 and Firefox < 9.0
// ref:
//  - https://bugs.webkit.org/show_activity.cgi?id=38995 //  - https://bugzilla.mozilla.org/show_bug.cgi?id=185236 //  - https://developer.mozilla.org/en/HTML/Element/link#Stylesheet_load_events var isOldWebKit = +navigator.userAgent
.replace(/.*AppleWebKit\/(\d+)\..*/, "$1") < 536

function request(url, callback, charset) {
var isCSS = IS_CSS_RE.test(url)
var node = doc.createElement(isCSS ? "link" : "script")

if (charset) {
var cs = isFunction(charset) ? charset(url) : charset
if (cs) {
node.charset = cs
}
}

addOnload(node, callback, isCSS, url)

if (isCSS) {
node.rel = "stylesheet"
node.href = url
}
else {
node.async = true
node.src = url
}

// For some cache cases in IE 6-8, the script executes IMMEDIATELY after
// the end of the insert execution, so use `currentlyAddingScript` to
// hold current node, for deriving url in `define` call
currentlyAddingScript = node

// ref: #185 & http://dev.jquery.com/ticket/2709 baseElement ?
head.insertBefore(node, baseElement) :
head.appendChild(node)

currentlyAddingScript = null
}

function addOnload(node, callback, isCSS, url) {
var supportOnload = "onload" in node

// for Old WebKit and Old Firefox
if (isCSS && (isOldWebKit || !supportOnload)) {
setTimeout(function() {
pollCss(node, callback)
}, 1) // Begin after node insertion
return
}

if (supportOnload) {
node.onload = onload
node.onerror = function() {
emit("error", { uri: url, node: node })
onload()
}
}
else {
node.onreadystatechange = function() {
if (/loaded|complete/.test(node.readyState)) {
onload()
}
}
}

function onload() {
// Ensure only run once and handle memory leak in IE
node.onload = node.onerror = node.onreadystatechange = null

// Remove the script to reduce memory leak
if (!isCSS && !data.debug) {
head.removeChild(node)
}

// Dereference the node
node = null

callback()
}
}

function pollCss(node, callback) {
var sheet = node.sheet
var isLoaded

// for WebKit < 536
if (isOldWebKit) {
if (sheet) {
isLoaded = true
}
}
// for Firefox < 9.0
else if (sheet) {
try {
if (sheet.cssRules) {
isLoaded = true
}
} catch (ex) {
// The value of `ex.name` is changed from "NS_ERROR_DOM_SECURITY_ERR"
// to "SecurityError" since Firefox 13.0. But Firefox is less than 9.0
// in here, So it is ok to just rely on "NS_ERROR_DOM_SECURITY_ERR"
if (ex.name === "NS_ERROR_DOM_SECURITY_ERR") {
isLoaded = true
}
}
}

setTimeout(function() {
if (isLoaded) {
// Place callback here to give time for style rendering
callback()
}
else {
pollCss(node, callback)
}
}, 20)
}

function getCurrentScript() {
if (currentlyAddingScript) {
return currentlyAddingScript
}

// For IE6-9 browsers, the script onload event may not fire right
// after the script is evaluated. Kris Zyp found that it
// could query the script nodes and the one that is in "interactive"
// mode indicates the current script
// ref: http://goo.gl/JHfFW if (interactiveScript && interactiveScript.readyState === "interactive") {
return interactiveScript
}

var scripts = head.getElementsByTagName("script")

for (var i = scripts.length - 1; i >= 0; i--) {
var script = scripts[i]
if (script.readyState === "interactive") {
interactiveScript = script
return interactiveScript
}
}
}

// For Developers
seajs.request = request

request函数：对url进行异步请求，请求完毕执行回调函数

addOnload函数：设置载入完毕后的回调动作，根据css，js以及浏览器是否是老版本，是否支持onload事件等情况进行区分处理，如果是css文件并且是老版本浏览器或者不支持onload，则使用一个定时器循环的来判断css是否载入完成(pollCSS),如果是js并且支持onload和不支持onload分两种情况进行了处理，最终目的是载入资源文件后能及时回调函数

pollCSS函数：判断css文件是否载入完成的函数，如果没有使用定时器不停的去判断，直到载入完成。

getCurrentScript函数：获取当前插入的javascript，在IE6-9浏览器中，script的onload事件有时候并不能在script加载后触发，需要遍历script的节点才能知道，当前脚本状态为 'interactive'

config.js

/**
* config.js - The configuration for the loader
*/

var BASE_RE = /^(.+?\/)(\?\?)?(seajs\/)+/

// The root path to use for id2uri parsing
// If loaderUri is `http://test.com/libs/seajs/[??][seajs/1.2.3/]sea.js`, the
// baseUri should be `http://test.com/libs/`
data.base = (loaderDir.match(BASE_RE) || ["", loaderDir])[1]

// The loader directory
data.dir = loaderDir

// The current working directory
data.cwd = cwd

// The charset for requesting files
data.charset = "utf-8"

// Modules that are needed to load before all other modules
data.preload = (function() {
var plugins = []

// Convert `seajs-xxx` to `seajs-xxx=1`
// NOTE: use `seajs-xxx=1` flag in uri or cookie to preload `seajs-xxx`
var str = location.search.replace(/(seajs-\w+)(&|$)/g, "$1=1$2")

// Add cookie string
str += " " + doc.cookie

// Exclude seajs-xxx=0
str.replace(/(seajs-\w+)=1/g, function(m, name) {
plugins.push(name)
})

return plugins
})()

// data.alias - An object containing shorthands of module id
// data.paths - An object containing path shorthands in module id
// data.vars - The {xxx} variables in module id
// data.map - An array containing rules to map module uri
// data.debug - Debug mode. The default value is false

seajs.config = function(configData) {

for (var key in configData) {
var curr = configData[key]
var prev = data[key]

// Merge object config such as alias, vars
if (prev && isObject(prev)) {
for (var k in curr) {
prev[k] = curr[k]
}
}
else {
// Concat array config such as map, preload
if (isArray(prev)) {
curr = prev.concat(curr)
}
// Make sure that `data.base` is an absolute path
else if (key === "base") {
// Make sure end with "/"
if (curr.slice(-1) !== "/") {
curr += "/"
}
curr = addBase(curr)
}

// Set config
data[key] = curr
}
}

emit("config", configData)
return seajs
}

config.js的主要功能就是设置一些基本配置，包括base路径，当前路径，预加载模块列表等，最主要的功能还是config方法，把用户传入的自定义配置设置到seajs中去。