null和undefined分别表示不同的概念:undefined是变量未初始化时的默认值,而null表示空对象引用,需显式赋值。两者类型不同,相等性比较结果也不同。 1. **定义差异**: - `undefined`表示变量已声明但未被赋值(如`let a;`),或函数未显式返回值时的默认值。 - `null`需主动赋值(如`let a = null;`),用...
Undefined是声明但未赋值的变量或未提供的函数参数默认值,null是赋值表示有意缺少对象值。 1. **定义差异** - `undefined`:当变量已声明但未初始化,或函数参数未传入时,变量自动获得此值。属于未定义状态的类型标识。 - `null`:需显式赋值,表示“无对象”的占位符,常用于主动标记应空缺的对象引用。 2. ...
In JavaScript, null and undefined are two special values that indicate the absence of a value. Although they are often used interchangeably, there is a subtle difference between them. What is undefined in JavaScript? undefined is a value automatically assigned to variables that have not been init...
Since we cannot find a number x, such that nx= -r, where n and r are integers; we would say the logarithm of a negative number is undefined. Mathematically, “undefined” can be defined as an expression which is impossible, or an expression which does not have an exact definition, or ...
console.log("the value of foo is: " + foo); // ReferenceError: foo is not defined In Example # 2, when we attempt to determine what type “undefined” is, we are told that it is of the type “undefined”. Hence, there is only one instance of the “undefined” value, and it ha...
As adjectives the difference between adolescent and undefined is that adolescent is characteristic]] of, or relating to, or [[undergo|undergoing adolescence; immature while undefined is...
Explain the difference between chemically defined and undefined (complex) media, giving specific examples. Culture Media: Culture media are used to grow bacteria, fungi, and others. Culture media provide the optimal conditions for the growth of microorganisms. Culture Medi...
Difference Between Undefined and InfinityWe affirm that a mathematical expression is undefined when we have a0 or something that doesn't exist. But infinity means no end, that is, too large to have an end. Therefore, undefined and infinity have different means....
What is the difference between 'undefined' and 'unsupplied' values?The undefined value is assigned to any variable or array element that has been declared but has not been assigned a value yet.If you create a variable 'a' but do not use the assignment operator '=' to store a value in...
The meaning of undefined is to say that a variable has declared, but it has no value assigned.let age //age is undefinedlet age = null //age is nullNote: accessing a variable that’s not been declared will raise a ReferenceError: <variable> is not defined error, but this does not ...