在JavaScript中,可以使用条件语句和逻辑运算符来检查一个值是否为空或null。以下是几种常见的方法: 1. 使用条件语句: - 使用if语句判断值是否为null或undefined: ...
constemptyObject={};if(!emptyObject){console.log("The object is null or undefined.");}elseif(Object.keys(emptyObject).length===0){console.log("The object is empty.");}else{console.log("The object is not empty.");}// Output: "The object is empty." 在上面的代码中,我们首先使用逻辑...
output =true;elseoutput =false;document.querySelector('.output-empty').textContent= output;if(typeofnonExistantArray !="undefined"&& nonExistantArray !=null&& nonExistantArray.length!=null&& nonExistantArray.length>0) output =true;elseoutput =false;document.querySelector('.output-non').textConten...
constobj1 = {};console.log(isObjectEmptyOrNull(obj1));// trueconstobj2 =null;console.log(isObjectEmptyOrNull(obj2));// trueconstobj3 = {name:"John",age:25};console.log(isObjectEmptyOrNull(obj3));// falseconstobj4 =undefined;console.log(isObjectEmptyOrNull(obj4));// true 总结...
Boolean: true or false Number: 1, 6.7, 0xFF String: "Gorilla and banana" Symbol: Symbol("name") (starting ES2015) Null: null Undefined: undefined. And a separated object type: {name: "Dmitri"}, ["apple", "orange"]. 从6个基本类型undefined是一个特殊的值,它的类型为Undefined。根据[ECM...
cash;}var account = new Account(100.50);console.log(account.cash); // 100.50console.log(account.hasMoney); // truevar emptyAccount = new Account(0);console.log(emptyAccount.cash); // 0console.log(emptyAccount.hasMoney); // false 该例中，如果account.cash的值大于零，那么account.has...
在上面的代码中,添加了额外的检查。这意味着如果它不是空对象,它将返回nullorundefined,如下例所示: let userDetails = { name: "John Doe", username: "jonnydoe", age: 14 }; let myEmptyObj = {}; let nullObj = null; let undefinedObj; ...
ECMAScirpt5 中 Array 类中的 filter 方法使用目的是移除所有的 ”false“ 类型元素 (false, null, undefined, 0, NaN or an empty string): letarr = [3,4,5,2,3,undefined,null,0,""];letarrNew = arr.filter(Boolean);console.log(arrNew)// [3, 4,...
Boolean: true or false Number: 1, 6.7, 0xFF String: "Gorilla and banana" Symbol: Symbol("name") (starting ES2015) Null: null Undefined: undefined. And a separatedobject type: {name: "Dmitri"}, ["apple", "orange"]. 从6个基本类型undefined...
function isEmpty(obj){ if(typeof obj == "undefined" || obj == null || obj == ""){ return true; }else{ return false; } } 1. 2. 3. 4. 5. 6. 7. 参考二: if (variable1 !== null || variable1 !== undefined || variable1 !== '') { ...