Function genHandler

static/vuejs/vue.common.js:8395–8443

(
  name,
  handler
)

}

function genHandler (
  name,
  handler
) {
  if (!handler) {
    return 'function(){}'
  }

  if (Array.isArray(handler)) {
    return ("[" + (handler.map(function (handler) { return genHandler(name, handler); }).join(',')) + "]")
  }

  var isMethodPath = simplePathRE.test(handler.value);
  var isFunctionExpression = fnExpRE.test(handler.value);

  if (!handler.modifiers) {
    return isMethodPath || isFunctionExpression
      ? handler.value
      : ("function($event){" + (handler.value) + "}") // inline statement
  } else {
    var code = '';
    var genModifierCode = '';
    var keys = [];
    for (var key in handler.modifiers) {
      if (modifierCode[key]) {
        genModifierCode += modifierCode[key];
        // left/right
        if (keyCodes[key]) {
          keys.push(key);
        }
      } else {
        keys.push(key);
      }
    }
    if (keys.length) {
      code += genKeyFilter(keys);
    }
    // Make sure modifiers like prevent and stop get executed after key filtering
    if (genModifierCode) {
      code += genModifierCode;
    }
    var handlerCode = isMethodPath
      ? handler.value + '($event)'
      : isFunctionExpression
        ? ("(" + (handler.value) + ")($event)")
        : handler.value;
    return ("function($event){" + code + handlerCode + "}")
  }
}

function genKeyFilter (keys) {
  return ("if(!('button' in $event)&&" + (keys.map(genFilterCode).join('&&')) + ")return null;")