console.log("numberZero有值,不为empty") }if(!boolFalse) { console.log("boolFalse没值,为empty"); }else{ console.log("boolFalse有值,不为empty"); } 测试结果如下: ref:https://www.delftstack.com/howto/javascript/javascript-check-if-string-is-empty/...
alert(typeof null);//object function check(value) { if ('string' == typeof value) { kongge1(value); kongge2(value); } else { console.log(typeof value); console.log('请输入字符串'); } } /* 使用String.trim()函数,来判断字符串是否全为空*/ function kongge1(test) { let str =...
Learn how to check if an input field is empty in React using different methods, such as empty string validation, react hook form, and JavaScript. This tutorial will show you how to handle empty field validation in React JS with examples
// Longhand if (test1 === true) or if (test1 !== "") or if (test1 !== null) // Shorthand //it will check empty string,null and undefined too if (test1) 注意:如果 test1 有任何值,它将在 if 循环后进入逻辑,该运算符主要用于 null 或undefined 的检查。 10.多个条件的 AND(&&)运...
字符串类型函数(String Functions) 顾名思义,字符串类型的函数肯定是针对字符串类型的参数、变量进行处理操作的函数 日期转字符串(date2str) 日期转字符串函数date2str主要有4个方法,分别是: date2str(date):传入日期实例,转换成字符串类型 date2str(date,format):传入日期和格式化参数,进行格式化转换 ...
log(`Hmm.. You don't have an age I guess`) } } checkAge({ age: 18 }) A: You are an adult! B: You are still an adult. C: Hmm.. You don't have an age I guess 答案: C 在测试相等性时,基本类型通过它们的值(value)进行比较,而对象通过它们的引用(reference)进行比较。JavaScript...
fromCharCode() 方法允许我们将 Unicode 值转换为人类可以阅读的可读字符。 由于此方法是 String 对象的一部分,我们使用关键字 String 访问它。 下面是一个例子: 如果你想使用 JavaScript 将字符串从二进制转换为普通文本,则此方法非常有用。 7. replaceAll()方法 ...
With the constructor, you can check if an object is aDate: Example (myDate.constructor=== Date); Try it Yourself » All Together typeof"John"// Returns "string" typeof("John"+"Doe")// Returns "string" typeof3.14// Returns "number" ...
data-basemap "<String>" Current basemap. data-loaded "" (empty string) Added to the map container after the map is loaded. data-scale "<Number>" Current map scale. data-updating "" (empty string) Added to the map container when the map is updating. data-zoom "<Number>" Current map...
if(x.trim() =="")throw"is empty"; if(isNaN(x))throw"is not a number"; x = Number(x); if(x >10)throw"is too high"; if(x <5)throw"is too low"; } catch(err){ message.innerHTML="Error: "+ err +"."; } finally{ ...