javascript 判断是否为数组

var isArray = function(a){
return a &&
typeof a === 'object' &&
typeof a.length === 'number' &&
typeof a.splice === 'function' &&
!(a.propertyIsEnumerable('length'));
}

var isArray = function(v){
return Object.prototype.toString.apply(v) === '[object Array]';
}

var isArray = function(object) {
return object != null && typeof object === "object" &&
'splice' in object && 'join' in object;
}