function bigFunction() { // code... myVariable; // => undefined // code... var myVariable = 'Initial value'; // code... myVariable; // => 'Initial value'}bigFunction(); 而使用 let 或者 const 进行变量声明则不会存在作用域提升的问题，因为变量在声明之前处于一个暂时性死...
英文:In this math problem, the value of x is undefined. 中文:由于缺少必要的参数,这个函数返回了一个未定义的结果。英文:Due to the lack of necessary parameters, this function returned an undefined result. 中文:这个术语在当前的上下文中是未定义的,我们需要更多的信息来...
John was working on a math problem, but he encountered a variable that was undefined. He couldn't solve the problem without knowing its value, so he decided to ask his teacher for help. (约翰正在做一道数学题,但他遇到了一个未定义的变量。他不知道这个变量的值,就无法解决问题,于是他决定向老...
More examples below. Description The undefined property indicates that a variable has not been assigned a value, or not declared at all. Browser Support undefined()is an ECMAScript1 (JavaScript 1997) feature. It is supported in all browsers: ...
The Undefined type has exactly one value, called undefined. Any variable that has not been assigned a value has the value undefined. 根据标准定义,当访问任何未被赋值的变量时均将返回undefined值。例如访问未初始化的变量、对象未定义的属性或者不存在的数组元素等: ...
Identify the math term described. Less than zero; minus. Determine the values of x for which the expression is undefined. \frac{1}{2x^2 - 50} 1. What happens to the value of \ln (x) as x approaches zero? What does zero measure mean? Why is \tan(\frac{\pi}{2})}] undefined ...
从6个基本类型undefined是一个特殊的值,它的类型为Undefined。根据[ECMAScript规范](https://www.ecma-international.org/ecma-262/7.0/#sec-undefined-value): 未定义的值原始值在变量未被赋值时使用。 该标准明确规定,在访问未初始化的变量,不存在的对象属性,不存在的数组元素等时,您将收到未定义的值。
在JavaScript 中有 Undefined (type)、undefined (value) 和 undefined (variable)。 Undefined (type) 是 JavaScript 的内置类型。 undefined (value) 是 Undefined 类型的唯一的值。任何未被赋值的属性都被假定为undefined(ECMA 4.3.9 和 4.3.10)。没有return语句的函数,或者return空的函数将返回undefined。函数中...
Undefined value primitive value is used when a variable has not been assigned a value. 当一个变量(声明后)没有被赋值时,这个变量的值会被默认为undefined。 标准明确规定,当您访问未初始化的变量,或者不存在的对象属性、数组元素等等,您会得到一个值undefined。例如: ...
在JavaScript 中有 Undefined (type)、undefined (value) 和 undefined (variable)。 Undefined (type) 是 JavaScript 的内置类型。 undefined (value) 是 Undefined 类型的唯一的值。任何未被赋值的属性都被假定为undefined(ECMA 4.3.9 和 4.3.10)。没有return语句的函数,或者return空的函数将返回undefined。函数中...