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...
unction allyIlliterate() { //tuce is *not* visible out here for( 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 he...
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...
// 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...
/* 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...
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 ...
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...
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...
// 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 a -> Uncaught SyntaxError: Missing initializer in const declarationconst a = 0// a = 1 -> Uncaught TypeError: Assignment to constant variable. 注意哦,这里所说的不能修改,并不是说变量的值不可修改,而是变量的标识符不能重新分配 ...