review
The last course talked about the initialization process of the Vue object. The first is to call the core _init() method, in which option is mounted to the VM object, and the life cycle, data, etc., is initialized. Finally, $mount method is used to mount the DOM object bound by EL. This section will look at the implementation of the $mount function.
- Get the EL object, convert the template to the Render function, and mount it by calling the top-level mount method
src/platform/web/entry-runtime-with-compiler.js
const mount = Vue.prototype.$mount
Vue.prototype.$mount = function (
el?: string | Element,
hydrating?: boolean
) :Component {
el = el && query(el)
/* istanbul ignore if */
if (el === document.body || el === document.documentElement) { process.env.NODE_ENV ! = ='production' && warn(
`Do not mount Vue to <html> or <body> - mount to normal elements instead.`
)
return this
}
const options = this.$options
// resolve template/el and convert to render function
if(! options.render) {let template = options.template
if (template) {
if (typeof template === 'string') {
if (template.charAt(0) = = =The '#') {
template = idToTemplate(template)
/* istanbul ignore if */
if(process.env.NODE_ENV ! = ='production' && !template) {
warn(
`Template element not found or is empty: ${options.template}`.this)}}}else if (template.nodeType) {
template = template.innerHTML
} else {
if(process.env.NODE_ENV ! = ='production') {
warn('invalid template option:' + template, this)}return this}}else if (el) {
template = getOuterHTML(el)
}
if (template) {
/* istanbul ignore if */
if(process.env.NODE_ENV ! = ='production' && config.performance && mark) {
mark('compile')}const { render, staticRenderFns } = compileToFunctions(template, {
shouldDecodeNewlines,
shouldDecodeNewlinesForHref,
delimiters: options.delimiters,
comments: options.comments
}, this)
options.render = render
options.staticRenderFns = staticRenderFns
/* istanbul ignore if */
if(process.env.NODE_ENV ! = ='production' && config.performance && mark) {
mark('compile end')
measure(`vue The ${this._name} compile`.'compile'.'compile end')}}}return mount.call(this, el, hydrating)
}
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- Call the mountComponent function
src/platform/web/runtime/index.js
Vue.prototype.$mount = function (
el?: string | Element,
hydrating?: boolean
) :Component {
el = el && inBrowser ? query(el) : undefined
return mountComponent(this, el, hydrating)
}
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- Instantiate Watcher and execute the callback function
updateComponent()
perform_render()
with_update()
src/core/instance/lifecycle.js
export function mountComponent (vm: Component, el: ? Element, hydrating? : boolean) :Component {
vm.$el = el
if(! vm.$options.render) { vm.$options.render = createEmptyVNodeif(process.env.NODE_ENV ! = ='production') {
/* istanbul ignore if */
if ((vm.$options.template && vm.$options.template.charAt(0)! = =The '#') ||
vm.$options.el || el) {
warn(
'You are using the runtime-only build of Vue where the template ' +
'compiler is not available. Either pre-compile the templates into ' +
'render functions, or use the compiler-included build.',
vm
)
} else {
warn(
'Failed to mount component: template or render function not defined.',
vm
)
}
}
}
callHook(vm, 'beforeMount')
let updateComponent
/* istanbul ignore if */
if(process.env.NODE_ENV ! = ='production' && config.performance && mark) {
updateComponent = () = > {
const name = vm._name
const id = vm._uid
const startTag = `vue-perf-start:${id}`
const endTag = `vue-perf-end:${id}`
mark(startTag)
const vnode = vm._render()
mark(endTag)
measure(`vue ${name} render`, startTag, endTag)
mark(startTag)
vm._update(vnode, hydrating)
mark(endTag)
measure(`vue ${name} patch`, startTag, endTag)
}
} else {
updateComponent = () = > {
vm._update(vm._render(), hydrating)
}
}
// we set this to vm._watcher inside the watcher's constructor
// since the watcher's initial patch may call $forceUpdate (e.g. inside child
// component's mounted hook), which relies on vm._watcher being already defined
new Watcher(vm, updateComponent, noop, {
before () {
if (vm._isMounted) {
callHook(vm, 'beforeUpdate')}}},true /* isRenderWatcher */)
hydrating = false
// manually mounted instance, call mounted on self
// mounted is called for render-created child components in its inserted hook
if (vm.$vnode == null) {
vm._isMounted = true
callHook(vm, 'mounted')}return vm
}
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Tips: The _render() function generates the virtual DOM and then passes it to _update() to update the final DOM. The updateComponent() function is actually executed for data updates and so on