js constresult=/(a+)(b+)(c+)/.exec("aaabcc");var[,a,b,c]=result;console.log(a,b,c);// "aaa" "b" "cc" 有关更多信息,请参阅解构。 Specification ECMAScript® 2026 Language Specification #sec-variable-statement 浏览器兼容性 ...
unction allyIlliterate() {//tuce is *not* visible out herefor( let tuce = 0; tuce < 5; tuce++) {//tuce is only visible in here (and in the for() parentheses)//and there is a separate tuce variable for each iteration of the loop}//tuce is *not* visible out here}function...
在javascript中,window.function(){}和var variable = function有什么区别? 声明变量"id"和"NSObject*"之间有什么区别? 在objective-C中,Type*var和Type*var之间有什么区别? 在函数中声明不带var的变量 在R的对象中,$和attr(,var)有什么区别? Scala中var和val定义有什么区别? 在JavaScript中声明多个...
// 未初始化 const a // 运行报错: Uncaught SyntaxError: Missing initializer in const declaration </script> 1. 2. 3. 4. <script> // 对常量做修改 const a = 1 a = 2; // 运行报错: Uncaught TypeError: Assignment to constant variable. </script> 1. 2. 3. 4. 5. 4. 使用 var 定义...
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...
/* 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...
I've heard that it's described as alocalvariable, but I'm still not quite sure how it behaves differently than thevarkeyword. What are the differences?. When shouldletbe used instead ofvar? 回答1 The difference is scoping.varis scoped to the nearest function block andletis scoped to the...
JavaScript 引擎会为for 循环中的let 声明分别创建独立的变量实例,虽然const 变量跟let 变量很相似,但是不能用const 来声明迭代变量(因为迭代变量会自增)。 for (const i = 0; i < 5; i++) { // TypeError: Assignment to constant variable. // nothing to do here. } 不过,如果你只想用const 声明一...
// 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...
a = "variable" b = 'change' // TypeError: Assignment to constant variable 如何理解声明之后不允许改变其值? 其实const 其实保证的不是变量的值不变,而是保证变量指向的内存地址所保存的数据不允许改动(即栈内存在的值和地址)。 JavaScript 的数据类型分为两类:原始值类型和对象(Object类型)。