jQuery分析(3) - jQuery.fn.init

// 多标签
parsed = buildFragment( [ data ], context, scripts );

/*
buildFragment 重要的参数是前面3个
elems     一个待转换的html字符串
context   转换上下文
scripts   是否忽略script标签
*/
function buildFragment(elems, context, scripts, selection, ignored) {
    var j, elem, contains,
        tmp, tag, tbody, wrap,
        l = elems.length,

        // Ensure a safe fragment
        // 创建文档碎片
        safe = createSafeFragment(context),

        nodes = [],
        i = 0;
    for (; i < l; i++) {
        elem = elems[i];

        if (elem || elem === 0) {

            // Add nodes directly
            // 如果在elems中的某个数组元素是对象直接添加到nodes
            if (jQuery.type(elem) === "object") {
                jQuery.merge(nodes, elem.nodeType ? [elem] : elem);

                // Convert non-html into a text node
                // 转换非html的字符串为文本节点
            } else if (!rhtml.test(elem)) {
                nodes.push(context.createTextNode(elem));

                // Convert html into DOM nodes
            } else {
                //给文档碎片创建一个元素，用来装接下来我们需要的html字符串
                tmp = tmp || safe.appendChild(context.createElement("div"));

                // Deserialize a standard representation
                // 取得标签名称，并转为小写
                tag = (rtagName.exec(elem) || ["", ""])[1].toLowerCase();
                // 需要其他元素包裹的标签
                wrap = wrapMap[tag] || wrapMap._default;
                //把我们的html字符串放入刚刚创建文档碎片的div中形成dom元素
                // 如果需要包裹元素则把html字符串进行包裹 <td>123</td> => <table><tbody><tr><td>abc</td></tr></tbody></table>
                tmp.innerHTML = wrap[1] + jQuery.htmlPrefilter(elem) + wrap[2];

                // Descend through wrappers to the right content
                // 取得刚刚创建的元素
                j = wrap[0];
                while (j--) {
                    tmp = tmp.lastChild;
                }

                // Manually add leading whitespace removed by IE
                if (!support.leadingWhitespace && rleadingWhitespace.test(elem)) {
                    nodes.push(context.createTextNode(rleadingWhitespace.exec(elem)[0]));
                }

                // Remove IE‘s autoinserted <tbody> from table fragments
                if (!support.tbody) {

                    // String was a <table>, *may* have spurious <tbody>
                    elem = tag === "table" && !rtbody.test(elem) ?
                        tmp.firstChild :

                        // String was a bare <thead> or <tfoot>
                        wrap[1] === "<table>" && !rtbody.test(elem) ?
                        tmp :
                        0;

                    j = elem && elem.childNodes.length;
                    while (j--) {
                        if (jQuery.nodeName((tbody = elem.childNodes[j]), "tbody") &&
                            !tbody.childNodes.length) {

                            elem.removeChild(tbody);
                        }
                    }
                }
                // 把创建好的dom节点也就是tmp的子节点合并到nodes中
                jQuery.merge(nodes, tmp.childNodes);

                // Fix #12392 for WebKit and IE > 9
                tmp.textContent = "";

                // Fix #12392 for oldIE
                while (tmp.firstChild) {
                    tmp.removeChild(tmp.firstChild);
                }

                // Remember the top-level container for proper cleanup
                tmp = safe.lastChild;
            }
        }
    }

    // Fix #11356: Clear elements from fragment
    // 清除文档碎片中的元素
    if (tmp) {
        safe.removeChild(tmp);
    }

    // Reset defaultChecked for any radios and checkboxes
    // about to be appended to the DOM in IE 6/7 (#8060)
    if (!support.appendChecked) {
        jQuery.grep(getAll(nodes, "input"), fixDefaultChecked);
    }

    i = 0;
    while ((elem = nodes[i++])) {

        // Skip elements already in the context collection (trac-4087)
        if (selection && jQuery.inArray(elem, selection) > -1) {
            if (ignored) {
                ignored.push(elem);
            }

            continue;
        }
        // 元素是否已经包含在document中
        contains = jQuery.contains(elem.ownerDocument, elem);

        // Append to fragment
        // 将创建好的元素再次添加到文档碎片中，并取得scirpt标签
        tmp = getAll(safe.appendChild(elem), "script");

        // Preserve script evaluation history
        if (contains) {
            setGlobalEval(tmp);
        }

        // Capture executables
        // 收集要执行的脚本
        if (scripts) {
            j = 0;
            while ((elem = tmp[j++])) {
                if (rscriptType.test(elem.type || "")) {
                    scripts.push(elem);
                }
            }
        }
    }

    tmp = null;
    // 返回创建好的文档碎片
    return safe;
}