You can test if an object exists by testing if the type isundefined: Example: if(typeofmyObj ==="undefined") Try it Yourself » But you cannot test if an object isnull, because this will throw an error if the object isundefined: ...
exports.Hello = Hello; 此时获取 Hello 对象require('./singleobject').Hello,略显冗余,可以用下面方法简化。 // hello.jsfunctionHello(){varname;this.setName =function(thyName){name = thyName;};this.sayHello =function(){console.log('Hello...
// Sample object var myCar = { make: "Ford", model: "Mustang", year: 2021 }; // Test if a key exists in the object if("model" in myCar === true) { alert("The specified key exists in the object."); } else { alert("The specified key doesn't exist in the object."); ...
/*判断数组中是否存在*/Array.prototype.exists=function(val) {for(vari = 0; i <this.length; i++) {if(this[i] ==val) {returntrue; } }returnfalse; }varthick = 0.4;varsurface = '喷锡';varpnlwidth = 18;varpnlheight = 24;//判断当板厚<=0.5mm,表面处理为喷锡时,PNL尺寸不能大于16X18...
createDirIfNotExists('test'); 3.currentURL:返回当前链接url const currentURL = () => window.location.href; currentURL(); // 'https://juejin.im' 4.distance:返回两点间的距离 该代码段通过计算欧几里得距离来返回两点之间的距离。 const distance = (x0, y0, x1, y1) => Math.hypot(x1 - x0...
自己运行生成test.db,和html页面放在同一目录下: PRAGMA foreign_keys=false;-- --- Table structure for sys_user-- ---DROPTABLEIFEXISTS"sys_user";CREATETABLE"sys_user" ( "id"bigint(11)NOTNULL, "role_id"bigint(11)NOTNULL, "user_name"varchar(255...
if ('name' in jsonObject) { console.log('对象中存在name属性'); } else { console.log('对象中不存在name属性'); } 另外,你还可以使用hasOwnProperty()方法来检查对象自身是否具有指定的属性。该方法只检查对象自身的属性,不会检查继承的属性。 示例: 代码语言:txt 复制 if (jsonObject.hasOwnProperty...
only('should return the index when present', function() { // this test will also be run }); it('should return -1 if called with a non-Array context', function() { // this test will not be run }); }); }); You may also choose multiple suites:...
name {String} bucket name If bucket exists and not belong to current account, will throw BucketAlreadyExistsError. If bucket not exists, will create a new bucket and set it's ACL. [options] {Object} optional parameters [acl] {String} include private,public-read,public-read-write [...
async test() { try { const result = await otherAsyncFunction(); console.log(result); // output result } catch(e) { console.log(e); // Can catch errors if otherAsyncFunction() throws an error } } Object.values() 返回Object 自身属性的所有值,不包括继承的值。 const exampleObj = {...