jQuery源码学习（4）- 初始化函数

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		function init (selector,context,rootjQuery){	
                          var match,elem,ret,doc;

			// Handle $(""), $(null), $(undefined), $(false)
			if (!selector) {
				return this;//this = jQuery
			}

			// Handle $(DOMElement)
			if (selector.nodeType) {
				//alert(1);
				this.context = this[0] = selector;
				this.length = 1;
				return this;
			}

			// Handle HTML strings
			if ( typeof selector === "string") {
				if (selector.charAt(0) === "<" && selector.charAt(selector.length - 1) === ">" && selector.length >= 3) {
					// Assume that strings that start and end with <> are HTML and skip the regex check
					match = [null, selector, null];

				} else {
					match = rquickExpr.exec(selector);
				}

				// Match html or make sure no context is specified for #id
				if (match && (match[1] || !context)) {
					// HANDLE: $(html) -> $(array)
					if (match[1]) {
						context = context instanceof jQuery ? context[0] : context;
						doc = (context && context.nodeType ? context.ownerDocument || context : document );
						// scripts is true for back-compat
						selector = jQuery.parseHTML(match[1], doc, true);
						if (rsingleTag.test(match[1]) && jQuery.isPlainObject(context)) {
							this.attr.call(selector, context, true);
						}

						return jQuery.merge(this, selector);

						// HANDLE: $(#id)
					} else {
						elem = document.getElementById(match[2]);

						// Check parentNode to catch when Blackberry 4.6 returns
						// nodes that are no longer in the document #6963
						if (elem && elem.parentNode) {
							// Handle the case where IE and Opera return items
							// by name instead of ID
							if (elem.id !== match[2]) {
								return rootjQuery.find(selector);
							}

							// Otherwise, we inject the element directly into the jQuery object
							this.length = 1;
							this[0] = elem;
						}

						this.context = document;
						this.selector = selector;
						return this;
					}

					// HANDLE: $(expr, $(...))
				} else if (!context || context.jquery) {
					return (context || rootjQuery ).find(selector);

					// HANDLE: $(expr, context)
					// (which is just equivalent to: $(context).find(expr)
				} else {
					return this.constructor(context).find(selector);
				}

				// HANDLE: $(function)
				// Shortcut for document ready
			} else if (jQuery.isFunction(selector)) {
				return rootjQuery.ready(selector);
			}

			if (selector.selector !== undefined) {
				this.selector = selector.selector;
				this.context = selector.context;
			}

			return jQuery.makeArray(selector, this);
}

分析待写！