alert("is null"); } 1. 2. 3. 4. 5. exp 为 undefined 时,也会得到与 null 相同的结果,虽然 null 和 undefined 不一样。注意:要同时判断 null 和 undefined 时可使用本法。 代码如下: var exp = null; if (!exp) { alert("is null"); } 1. 2. 3. 4. 5. 如果exp 为 undefined,或数...
使用模板字符串或者使用String()包装时,preferedType=string,即优先调用.toString()。 例如: 代码语言:javascript 代码运行次数:0 运行 AI代码解释 [1,null,undefined,2].toString()// '1,,,2'// Uncaught TypeError: Cannot convert a Symbol value to a string[1,Symbol('x')].toString()// Uncaught Typ...
isEmptyObject([]) // false 1. 2. 3. 4. 5. 6. 7. ?但是要当心!下面这些值会引发错误。 // TypeError: Cannot covert undefined or null to object isEmptyObject(undefined); isEmptyObject(null); // TypeError: Cannot covert undefined or null to object isEmptyObject(undefined); isEmptyObject...
从Node.js进入我们的视野时,我们所知道的它就由这些关键字组成事件驱动、非阻塞I/O、高效、轻量,它在官网中也是这么描述自己的: Node.js® is a JavaScript runtime built on Chrome’s V8 JavaScript engine. Node.js uses an event-driven, non-blocking I/O model that makes it lightweight and effic...
updateForm(formId,bindingData); }catch(FormException e) { e.printStackTrace(); } break; } default: { Map<String, Object> result =newHashMap<String, Object>(); reply.writeString(ZSONObject.toZSONString(result)); returnfalse; } } returntrue; } }...
It defaults to no referrer (which reflects as the empty string). contentType affects the value read from document.contentType, as well as how the document is parsed: as HTML or as XML. Values that are not a HTML MIME type or an XML MIME type will throw. It defaults to "text/html"...
is-digit-string is-docker is-domain-name is-duration-string is-electron-main is-electron-renderer is-electron is-email-address is-empty-array-like-object is-empty-array is-empty-collection is-empty-object is-empty-string is-enumerable-property-in ...
Cannot provide null or empty named parameter name. DuplicateNamedParameter 5036 Duplicate named parameter. MissingNameParameter 5037 The specified named parameter name is not one of the formal parameters. MoreNamedParametersThanArguments 5038 Too few arguments specified. The number of named parameter names...
Delete an empty bucket.parameters:name {String} bucket name If bucket is not empty, will throw BucketNotEmptyError. If bucket is not exists, will throw NoSuchBucketError. [options] {Object} optional parameters [timeout] {Number} the operation timeout ...
答案是A。在MDN关于 null 的文档中也特别指出来了,typeof null 的结果是 "object",它是ECMAScript的bug,其实应该是 "null"。但这个bug由来已久,在JavaScript中已经存在了将近二十年,也许永远不会修复,因为这牵扯到太多的Web系统,修复它会产生更多的bug,令许多系统无法正常工作。