在使用 for 循环时，我们常常需要一个变量来控制循环的次数。通常，我们使用 let 来声明这个变量，因为 let 允许我们在循环中不断更新变量的值。然而，如果我们错误地使用了 const，会导致“Uncaught (in promise) TypeError: Assignment to constant variable.” 的错误。描述问题 考虑以下代码片段：这段代码在执行时...
/* 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 声明的变量是全局范...
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.
Uncaught TypeError: Assignment to constant variable. (3)声明后必须立即初始化 const PI; PI= 3.1415; console.log(PI); 报错: Uncaught SyntaxError: Missing initializer in const declaration (4)不允许在相同作用域内重复声明同一个变量的 const PI = 3.1415; console.log(PI); const PI= 3.1415926; conso...
错误:Assignment to constant variable.==》对常量变量赋值。 总结:const 用于声明一个或多个常量,声明时必须进行初始化,且初始化后值不可再修改 2、var 我们首先声明一个变量b,仅仅是声明: var b; console.log(`b is ${b}`); 1. 2. 运行结果: ...
// var var a = 10 a = 20 console.log(a) // 20 //let let b = 10 b = 20 console.log(b) // 20 // const const c = 10 c = 20 console.log(c) // Uncaught TypeError: Assignment to constant variable 使用 能用const的情况尽量使用const,其他情况下大多数使用let,避免使用var var let...
const prop = '哈哈'; prop = '嘻嘻' // 报错 Uncaught TypeError: Assignment to constant variable. 对于简单对象来说,内存地址就是值,即常量(一变就报错)。但是对于对象而言,对象本身不能重复赋值(变量指向的那个内存地址所保存的数据不得改动),但是可以给对象的属性重新赋值 const obj = {name: 'lxm'} ...
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...
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 ...
The var statement declares a variable in JavaScript which abides to the following rules: is function-scoped or globally-scoped. is not subject to the temporal dead zone. it creates a global property on window with the same name. is reassignable. is redeclarable. Function-scoped or globally-sc...