/* 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. What is the var Keyword? (200 words) The `var` keyword is used to declare a variable in JavaScript. Before the introduction of ES6 (ECMAScript 2015), `var` was the primary method for declaring variables in JavaScript. It follows a function scope or global scope, depending on where ...
:ReferenceError: a is not defined 全局变量a不用var申明就不会报错:a = 'global scope';function b (){ var a = 'local scope'; eval('console.log(a,1)'); //local scope (new Function('','console.log(a,2)'))(); //global scope }b();依次打印:local scope 1global scope 2javascript ...
In JavaScript, var, let, and const are used to declare variables, The main difference are as follows. Scope var: Variables declared with var are function scoped. They are visible throughout the whole function in which they are declared. If declared outside any function, they become globa...
var a = 11; // the scope is global let b = 22; // the scope is inside the if-block console.log(a); // 11 console.log(b); // 22 } console.log(a); // 11 console.log(b); // 2 const 常量必须在声明的同时指定它的值. ...
Scope of var: The scope specifies where we can access or use the variables. When we declare a variable outside a function, its scope is global. In other words, it means that the variables whose declaration happens with "var" outside a function (even within a block) are accessible in th...
javascript scope ecmascript-6 var let 答案区别在于范围界定。 var的作用范围是最接近的功能块和let可以被限制在最近的封闭块,其可以是比功能块小。如果在任何区域之外,两者都是全球 此外,使用let声明的变量在它们的封闭块中声明之前是不可访问的。如演示中所示,这将引发 ReferenceError 异常。 演示:...
vara = 1;varb = 2;if(a === 1) {vara = 11;//the scope is globallet b = 22;//the scope is inside the if-blockconsole.log(a);//11console.log(b);//22} console.log(a);//11console.log(b);//2 const 常量必须在声明的同时指定它的值. ...
What are var, let, and const in JavaScript? Var, let, and const are keywords that users use to declare and initialize variables. The 'var' keyword in JavaScript: Thevar is the oldest keyword in JavaScript. Global or function scope is the scope of the 'var' keyword. The scope of var ...
If you define the variable using the let keyword inside the block, which is inside the function, and try to access it outside the block, it will throw an error. JavaScript Global Scope It becomes the global variable if you define the variable using the 'var' keyword outside the function...