6, 45]. Like all arrays, the array elements in s are mutable, but because const was used, you cannot use the variable identifier s to point to a different array using the assignment operator.
下面是一个例子: /* This variable has a global scope, it's accessible everywhere */vargreeting ="Hello John";functionsayHelllo(){console.log(greeting);// "Hello John"}console.log(greeting);// "Hello John" 因此,在函数外部使用关键字 var ...
const VARIABLENAME = VALUE; For example, if we wanted to declare a variable called “pimylifeup” as a const while also assigning it the value “pimylifeup.com“, you would use the following code. const pimylifeup = "pimylifeup.com" A Const Variable cannot be Reassigned in JavaScript...
const obj = {name: 'lxm'} obj = {name: 'lxm love js'} // 报错 Uncaught TypeError: Assignment to constant variable. obj['name'] = 'lxm love js' // 不报错 一旦声明,必须马上赋值 let prop1; var prop2; // 不报错 const prop3 = '哈哈' const prop4; // 报错 Uncaught SyntaxError:...
这几天修改别人的js,发现声明变量有的用var,有的用let,那它们有什么区别呢? javascript中声明变量的方式有:var、let、const 1.var (1)作用域: 整个函数范围内,或者是全局的 functionfunc() {if(true) {varstr = 'hello world'; } console.log(str); ...
let varData = 'variable';const constData = 'constant';varData = 1;constData = true // Uncaught TypeError: Assignment to constant variable.const声明时必须进行初始化（let可以不进行初始化赋值）。let varData;const constData; // Uncaught SyntaxError: Missing initializer in const declaration const声明的...
const 对象 js 方法const ## What are const objects in JavaScript? In JavaScript, the `const` keyword can be used to create a constant variable. A constant variable cannot be reassigned, and it must be initialized with a value. Const objects are objects that are created using the `const` ...
age=31//15 Uncaught TypeError: Assignment to constant variable.需要注意的是const和let一样都是快作用域，也就是说在块语句外部声明的const变量不会印象在块语句内部声明的变量，反之亦然：const name="jsindexhtml"；if(true){ const name="hsindexhtml";//不会报错 } 当然，我们仅不能修改const定义的的...
Redeclaring a JavaScriptvarvariable is allowed anywhere in a program: Example varx =2;// Allowed varx =3;// Allowed x =4;// Allowed Redeclaring an existingvarorletvariable toconst, in the same scope, is not allowed: Example varx =2;// Allowed ...
Variable object:变量对象,用于存储被定义在执行上下文中的变量 (variables) 和函数声明 (function declarations) 。 Scope chain:作用域链,是一个对象列表 (list of objects) ,用以检索上下文代码中出现的标识符 (identifiers) 。 thisValue:this 指针,是一个与执行上下文相关的特殊对象,也被称之为上下文对象。