vue源码中parse就是把template解析为ast的过程。
AST
Abstract Syntax Tree（抽象语法树的意思）
比如
<div>test</div>
写为抽象语法树
{
tag:'div',
type :1 ,
children:[ {
type:3,
text:'test'
} ]
}
我们查看vue运行过程，可以找一个项目，在里面打上日志来进行。在dist目录下面vue.esm.js这个文件里面进行打log查看，
parse
主要流程在parse函数里面,源码如下
/**
* Convert HTML string to AST.
*/
function parse (
template,
options
) {
warn$2 = options.warn || baseWarn;
platformIsPreTag = options.isPreTag || no;
platformMustUseProp = options.mustUseProp || no;
platformGetTagNamespace = options.getTagNamespace || no;
transforms = pluckModuleFunction(options.modules, 'transformNode');
preTransforms = pluckModuleFunction(options.modules, 'preTransformNode');
postTransforms = pluckModuleFunction(options.modules, 'postTransformNode');
delimiters = options.delimiters;
var stack = [];
var preserveWhitespace = options.preserveWhitespace !== false;
var root;
var currentParent;
var inVPre = false;
var inPre = false;
var warned = false;
function warnOnce (msg) {
if (!warned) {
warned = true;
warn$2(msg);
}
}
function endPre (element) {
// check pre state
if (element.pre) {
inVPre = false;
}
if (platformIsPreTag(element.tag)) {
inPre = false;
}
}
parseHTML(template, {
warn: warn$2,
expectHTML: options.expectHTML,
isUnaryTag: options.isUnaryTag,
canBeLeftOpenTag: options.canBeLeftOpenTag,
shouldDecodeNewlines: options.shouldDecodeNewlines,
shouldKeepComment: options.comments,
start: function start (tag, attrs, unary) {
// check namespace.
// inherit parent ns if there is one
var ns = (currentParent && currentParent.ns) || platformGetTagNamespace(tag);
// handle IE svg bug
/* istanbul ignore if */
if (isIE && ns === 'svg') {
attrs = guardIESVGBug(attrs);
}
console.log('tag', tag)
console.log('attrs', attrs)
console.log('currentParent', currentParent)
var element = createASTElement(tag, attrs, currentParent);
console.log('element', element)
if (ns) {
element.ns = ns;
}
if (isForbiddenTag(element) && !isServerRendering()) {
element.forbidden = true;
process.env.NODE_ENV !== 'production' && warn$2(
'Templates should only be responsible for mapping the state to the ' +
'UI. Avoid placing tags with side-effects in your templates, such as ' +
"<" + tag + ">" + ', as they will not be parsed.'
);
}
// apply pre-transforms
for (var i = 0; i < preTransforms.length; i++) {
element = preTransforms[i](element, options) || element;
}
if (!inVPre) {
processPre(element);
if (element.pre) {
inVPre = true;
}
}
if (platformIsPreTag(element.tag)) {
inPre = true;
}
if (inVPre) {
processRawAttrs(element);
} else if (!element.processed) {
// structural directives
processFor(element);
processIf(element);
processOnce(element);
// element-scope stuff
processElement(element, options);
}
function checkRootConstraints (el) {
if (process.env.NODE_ENV !== 'production') {
if (el.tag === 'slot' || el.tag === 'template') {
warnOnce(
"Cannot use <" + (el.tag) + "> as component root element because it may " +
'contain multiple nodes.'
);
}
if (el.attrsMap.hasOwnProperty('v-for')) {
warnOnce(
'Cannot use v-for on stateful component root element because ' +
'it renders multiple elements.'
);
}
}
}
// tree management
if (!root) {
root = element;
checkRootConstraints(root);
} else if (!stack.length) {
// allow root elements with v-if, v-else-if and v-else
if (root.if && (element.elseif || element.else)) {
checkRootConstraints(element);
addIfCondition(root, {
exp: element.elseif,
block: element
});
} else if (process.env.NODE_ENV !== 'production') {
warnOnce(
"Component template should contain exactly one root element. " +
"If you are using v-if on multiple elements, " +
"use v-else-if to chain them instead."
);
}
}
if (currentParent && !element.forbidden) {
if (element.elseif || element.else) {
processIfConditions(element, currentParent);
} else if (element.slotScope) { // scoped slot
currentParent.plain = false;
var name = element.slotTarget || '"default"';(currentParent.scopedSlots || (currentParent.scopedSlots = {}))[name] = element;
} else {
currentParent.children.push(element);
element.parent = currentParent;
}
}
if (!unary) {
currentParent = element;
stack.push(element);
} else {
endPre(element);
}
// apply post-transforms
for (var i$1 = 0; i$1 < postTransforms.length; i$1++) {
postTransforms[i$1](element, options);
}
},
end: function end () {
// remove trailing whitespace
var element = stack[stack.length - 1];
var lastNode = element.children[element.children.length - 1];
if (lastNode && lastNode.type === 3 && lastNode.text === ' ' && !inPre) {
element.children.pop();
}
// pop stack
stack.length -= 1;
currentParent = stack[stack.length - 1];
endPre(element);
},
chars: function chars (text) {
if (!currentParent) {
if (process.env.NODE_ENV !== 'production') {
if (text === template) {
warnOnce(
'Component template requires a root element, rather than just text.'
);
} else if ((text = text.trim())) {
warnOnce(
("text \"" + text + "\" outside root element will be ignored.")
);
}
}
return
}
// IE textarea placeholder bug
/* istanbul ignore if */
if (isIE &&
currentParent.tag === 'textarea' &&
currentParent.attrsMap.placeholder === text
) {
return
}
var children = currentParent.children;
text = inPre || text.trim()
? isTextTag(currentParent) ? text : decodeHTMLCached(text)
// only preserve whitespace if its not right after a starting tag
: preserveWhitespace && children.length ? ' ' : '';
if (text) {
var expression;
if (!inVPre && text !== ' ' && (expression = parseText(text, delimiters))) {
children.push({
type: 2,
expression: expression,
text: text
});
} else if (text !== ' ' || !children.length || children[children.length - 1].text !== ' ') {
children.push({
type: 3,
text: text
});
}
}
},
comment: function comment (text) {
currentParent.children.push({
type: 3,
text: text,
isComment: true
});
}
});
console.log(root);
return root
}
主力是parseHTML这个函数，我们关键看这个函数
parseHTML(template, {
warn: warn$2,
expectHTML: options.expectHTML,
isUnaryTag: options.isUnaryTag,
canBeLeftOpenTag: options.canBeLeftOpenTag,
shouldDecodeNewlines: options.shouldDecodeNewlines,
shouldKeepComment: options.comments,
start: function start (tag, attrs, unary) {
// check namespace.
// inherit parent ns if there is one
var ns = (currentParent && currentParent.ns) || platformGetTagNamespace(tag);
// handle IE svg bug
/* istanbul ignore if */
if (isIE && ns === 'svg') {
attrs = guardIESVGBug(attrs);
}
console.log('tag', tag)
console.log('attrs', attrs)
console.log('currentParent', currentParent)
var element = createASTElement(tag, attrs, currentParent);
console.log('element', element)
if (ns) {
element.ns = ns;
}
if (isForbiddenTag(element) && !isServerRendering()) {
element.forbidden = true;
process.env.NODE_ENV !== 'production' && warn$2(
'Templates should only be responsible for mapping the state to the ' +
'UI. Avoid placing tags with side-effects in your templates, such as ' +
"<" + tag + ">" + ', as they will not be parsed.'
);
}
// apply pre-transforms
for (var i = 0; i < preTransforms.length; i++) {
element = preTransforms[i](element, options) || element;
}
if (!inVPre) {
processPre(element);
if (element.pre) {
inVPre = true;
}
}
if (platformIsPreTag(element.tag)) {
inPre = true;
}
if (inVPre) {
processRawAttrs(element);
} else if (!element.processed) {
// structural directives
processFor(element);
processIf(element);
processOnce(element);
// element-scope stuff
processElement(element, options);
}
function checkRootConstraints (el) {
if (process.env.NODE_ENV !== 'production') {
if (el.tag === 'slot' || el.tag === 'template') {
warnOnce(
"Cannot use <" + (el.tag) + "> as component root element because it may " +
'contain multiple nodes.'
);
}
if (el.attrsMap.hasOwnProperty('v-for')) {
warnOnce(
'Cannot use v-for on stateful component root element because ' +
'it renders multiple elements.'
);
}
}
}
// tree management
if (!root) {
root = element;
checkRootConstraints(root);
} else if (!stack.length) {
// allow root elements with v-if, v-else-if and v-else
if (root.if && (element.elseif || element.else)) {
checkRootConstraints(element);
addIfCondition(root, {
exp: element.elseif,
block: element
});
} else if (process.env.NODE_ENV !== 'production') {
warnOnce(
"Component template should contain exactly one root element. " +
"If you are using v-if on multiple elements, " +
"use v-else-if to chain them instead."
);
}
}
if (currentParent && !element.forbidden) {
if (element.elseif || element.else) {
processIfConditions(element, currentParent);
} else if (element.slotScope) { // scoped slot
currentParent.plain = false;
var name = element.slotTarget || '"default"';(currentParent.scopedSlots || (currentParent.scopedSlots = {}))[name] = element;
} else {
currentParent.children.push(element);
element.parent = currentParent;
}
}
if (!unary) {
currentParent = element;
stack.push(element);
} else {
endPre(element);
}
// apply post-transforms
for (var i$1 = 0; i$1 < postTransforms.length; i$1++) {
postTransforms[i$1](element, options);
}
},
end: function end () {
// remove trailing whitespace
var element = stack[stack.length - 1];
var lastNode = element.children[element.children.length - 1];
if (lastNode && lastNode.type === 3 && lastNode.text === ' ' && !inPre) {
element.children.pop();
}
// pop stack
stack.length -= 1;
currentParent = stack[stack.length - 1];
endPre(element);
},
chars: function chars (text) {
if (!currentParent) {
if (process.env.NODE_ENV !== 'production') {
if (text === template) {
warnOnce(
'Component template requires a root element, rather than just text.'
);
} else if ((text = text.trim())) {
warnOnce(
("text \"" + text + "\" outside root element will be ignored.")
);
}
}
return
}
// IE textarea placeholder bug
/* istanbul ignore if */
if (isIE &&
currentParent.tag === 'textarea' &&
currentParent.attrsMap.placeholder === text
) {
return
}
var children = currentParent.children;
text = inPre || text.trim()
? isTextTag(currentParent) ? text : decodeHTMLCached(text)
// only preserve whitespace if its not right after a starting tag
: preserveWhitespace && children.length ? ' ' : '';
if (text) {
var expression;
if (!inVPre && text !== ' ' && (expression = parseText(text, delimiters))) {
children.push({
type: 2,
expression: expression,
text: text
});
} else if (text !== ' ' || !children.length || children[children.length - 1].text !== ' ') {
children.push({
type: 3,
text: text
});
}
}
},
comment: function comment (text) {
currentParent.children.push({
type: 3,
text: text,
isComment: true
});
}
});
stack帮助理清节点关系
currentParent是当前标签的父节点
