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
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...
/*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...
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:...
// 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."); ...
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...
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...
function f() { if (condition) { var tmp = ...; ... } // tmp still exists here // => not what we want } 如果要为then块引入新的作用域,可以定义一个函数并立即调用它。这是一种解决方法,模拟块作用域: 代码语言:javascript 代码运行次数:0 运行 复制 function f() { if (condition) { ...
parse (default: {})— pass an object if you wish to specify some additional parse options. sourceMap (default: false)— pass an object if you wish to specify source map options. toplevel (default: false)— set to true if you wish to enable top level variable and function name mangling...
👎 Anti-Pattern Example: A test suite that passes due to non-realistic data const addProduct = (name, price) => { const productNameRegexNoSpace = /^\S*$/; //no white-space allowed if (!productNameRegexNoSpace.test(name)) return false; //this path never reached due to dull input...