@method: parseHTML
@params: html(vue中的template),options(特殊配置)
@return match(AST树)
例子：
html = “
1-2
”
1-3
1、进入while循环
2、记录第一个字符串<的位置，区分是否需要清楚文本内容
3、startTagOpen正则匹配标签的开始部分，包括了标签带有的属性
4、对匹配到的标签进行属性匹配，循环将并将属性添加到match.attr数组中。
5、每次匹配后都会用index记录当前位置，并将html向前移动指定位置
function parseHTML (html,options) {
const stack = [] const expectHTML = options.expectHTML const isUnaryTag = options.isUnaryTag || no const canBeLeftOpenTag = options.canBeLeftOpenTag || no let index = 0 let last, lastTag while (html) { last = html // Make sure we're not in a plaintext content element like script/style if (!lastTag || !isPlainTextElement(lastTag)) { let textEnd = html.indexOf('<') if (textEnd === 0) { // Comment: if (comment.test(html)) { const commentEnd = html.indexOf('-->') if (commentEnd >= 0) { if (options.shouldKeepComment) { options.comment(html.substring(4, commentEnd), index, index + commentEnd + 3) } advance(commentEnd + 3) continue } } // http://en.wikipedia.org/wiki/Conditional_comment#Downlevel-revealed_conditional_comment if (conditionalComment.test(html)) { const conditionalEnd = html.indexOf(']>') if (conditionalEnd >= 0) { advance(conditionalEnd + 2) continue } } // Doctype: const doctypeMatch = html.match(doctype) if (doctypeMatch) { advance(doctypeMatch[0].length) continue } // End tag: const endTagMatch = html.match(endTag) if (endTagMatch) { const curIndex = index advance(endTagMatch[0].length) parseEndTag(endTagMatch[1], curIndex, index) continue } // Start tag: const startTagMatch = parseStartTag() if (startTagMatch) { handleStartTag(startTagMatch) if (shouldIgnoreFirstNewline(startTagMatch.tagName, html)) { advance(1) } continue } } let text, rest, next if (textEnd >= 0) { rest = html.slice(textEnd) while ( !endTag.test(rest) && !startTagOpen.test(rest) && !comment.test(rest) && !conditionalComment.test(rest) ) { // < in plain text, be forgiving and treat it as text next = rest.indexOf('<', 1) if (next < 0) break textEnd += next rest = html.slice(textEnd) } text = html.substring(0, textEnd) } if (textEnd < 0) { text = html } if (text) { advance(text.length) } if (options.chars && text) { options.chars(text, index - text.length, index) } } else { let endTagLength = 0 const stackedTag = lastTag.toLowerCase() const reStackedTag = reCache[stackedTag] || (reCache[stackedTag] = new RegExp('([\\s\\S]*?)(</' + stackedTag + '[^>]*>)', 'i')) const rest = html.replace(reStackedTag, function (all, text, endTag) { endTagLength = endTag.length if (!isPlainTextElement(stackedTag) && stackedTag !== 'noscript') { text = text .replace(/<!\--([\s\S]*?)-->/g, '$1') // #7298 .replace(/<!\[CDATA\[([\s\S]*?)]]>/g, '$1') } if (shouldIgnoreFirstNewline(stackedTag, text)) { text = text.slice(1) } if (options.chars) { options.chars(text) } return '' }) index += html.length - rest.length html = rest parseEndTag(stackedTag, index - endTagLength, index) } if (html === last) { options.chars && options.chars(html) if (process.env.NODE_ENV !== 'production' && !stack.length && options.warn) { options.warn(`Mal-formatted tag at end of template: "${html}"`, { start: index + html.length }) } break } }
}
