上传vue源码，用来写注释。

Author: answershuto

vue-src/compiler/codegen/events.js

@@ -0,0 +1,121 @@
+/* @flow */
+
+const fnExpRE = /^\s*([\w$_]+|\([^)]*?\))\s*=>|^function\s*\(/
+const simplePathRE = /^\s*[A-Za-z_$][\w$]*(?:\.[A-Za-z_$][\w$]*|\['.*?']|\[".*?"]|\[\d+]|\[[A-Za-z_$][\w$]*])*\s*$/
+
+// keyCode aliases
+const keyCodes: { [key: string]: number | Array<number> } = {
+  esc: 27,
+  tab: 9,
+  enter: 13,
+  space: 32,
+  up: 38,
+  left: 37,
+  right: 39,
+  down: 40,
+  'delete': [8, 46]
+}
+
+// #4868: modifiers that prevent the execution of the listener
+// need to explicitly return null so that we can determine whether to remove
+// the listener for .once
+const genGuard = condition => `if(${condition})return null;`
+
+const modifierCode: { [key: string]: string } = {
+  stop: '$event.stopPropagation();',
+  prevent: '$event.preventDefault();',
+  self: genGuard(`$event.target !== $event.currentTarget`),
+  ctrl: genGuard(`!$event.ctrlKey`),
+  shift: genGuard(`!$event.shiftKey`),
+  alt: genGuard(`!$event.altKey`),
+  meta: genGuard(`!$event.metaKey`),
+  left: genGuard(`'button' in $event && $event.button !== 0`),
+  middle: genGuard(`'button' in $event && $event.button !== 1`),
+  right: genGuard(`'button' in $event && $event.button !== 2`)
+}
+
+export function genHandlers (
+  events: ASTElementHandlers,
+  native: boolean,
+  warn: Function
+): string {
+  let res = native ? 'nativeOn:{' : 'on:{'
+  for (const name in events) {
+    const handler = events[name]
+    // #5330: warn click.right, since right clicks do not actually fire click events.
+    if (process.env.NODE_ENV !== 'production' &&
+        name === 'click' &&
+        handler && handler.modifiers && handler.modifiers.right
+      ) {
+      warn(
+        `Use "contextmenu" instead of "click.right" since right clicks ` +
+        `do not actually fire "click" events.`
+      )
+    }
+    res += `"${name}":${genHandler(name, handler)},`
+  }
+  return res.slice(0, -1) + '}'
+}
+
+function genHandler (
+  name: string,
+  handler: ASTElementHandler | Array<ASTElementHandler>
+): string {
+  if (!handler) {
+    return 'function(){}'
+  }
+
+  if (Array.isArray(handler)) {
+    return `[${handler.map(handler => genHandler(name, handler)).join(',')}]`
+  }
+
+  const isMethodPath = simplePathRE.test(handler.value)
+  const isFunctionExpression = fnExpRE.test(handler.value)
+
+  if (!handler.modifiers) {
+    return isMethodPath || isFunctionExpression
+      ? handler.value
+      : `function($event){${handler.value}}` // inline statement
+  } else {
+    let code = ''
+    let genModifierCode = ''
+    const keys = []
+    for (const key in handler.modifiers) {
+      if (modifierCode[key]) {
+        genModifierCode += modifierCode[key]
+        // left/right
+        if (keyCodes[key]) {
+          keys.push(key)
+        }
+      } else {
+        keys.push(key)
+      }
+    }
+    if (keys.length) {
+      code += genKeyFilter(keys)
+    }
+    // Make sure modifiers like prevent and stop get executed after key filtering
+    if (genModifierCode) {
+      code += genModifierCode
+    }
+    const handlerCode = isMethodPath
+      ? handler.value + '($event)'
+      : isFunctionExpression
+        ? `(${handler.value})($event)`
+        : handler.value
+    return `function($event){${code}${handlerCode}}`
+  }
+}
+
+function genKeyFilter (keys: Array<string>): string {
+  return `if(!('button' in $event)&&${keys.map(genFilterCode).join('&&')})return null;`
+}
+
+function genFilterCode (key: string): string {
+  const keyVal = parseInt(key, 10)
+  if (keyVal) {
+    return `$event.keyCode!==${keyVal}`
+  }
+  const alias = keyCodes[key]
+  return `_k($event.keyCode,${JSON.stringify(key)}${alias ? ',' + JSON.stringify(alias) : ''})`
+}