functionletExample(){if(true){letz=30;console.log(z);// 输出: 30}// console.log(z); // 报错: ReferenceError: z is not defined,因为 z 是块级作用域变量}letExample();// 全局作用域中的 let(不推荐,应尽量减少全局变量)leta=40;functionyetAnotherFunction(){console.log(a);// 输出: 40}...
在JavaScript中,使用"let"和"var"声明变量的主要区别在于它们的作用域和生命周期。 1. 作用域: - "var"声明的变量具有函数作用域,这意味着如果在函数内部声明变量,它将在函...
因此,通过这种方式,我们不能使用块外的变量,因为使用 let 关键字声明的变量的范围仅限于块。 要查看 let 和var 之间的区别,请查看以下代码段: function example() { for (var i = 0; i < 10; i++) console.log(i); console.log(i); } example(); 在上面的代码中,我们可以观察到我们使用了 var...
在顶层,let与var不同,不会在全局对象上创建属性: var foo = "Foo"; // globally scoped let bar = "Bar"; // globally scoped but not part of the global object console.log(window.foo); // Foo console.log(window.bar); // undefined 重新声明 在严格模式下,var 允许在同一作用域内重新声明同...
var toDo = new ToDoClass(); }); If you were to accidentally re-declaretoDosomewhere along the code, as follows, your class object gets overwritten: var toDo = "some value"; This behavior is confusing and quite difficult to maintain variables for large applications. Hence,letwas introduced ...
1. Differences between var, let and const We will see the main differences in short, and then we will explain further in the post. Variables declared byvarandconstkeywords arefunction scopedand are scoped to the immediate function body. ...
Let`s look at two examples: eval and immediately invoked function expressions. 如果你需要以花括号或者 function 关键字开头书写表达式语句,应该如何处理呢?可以将表达式语句放在小括号中,既不会对执行结果产生影响,同时保证表达式语句出现在仅有表达式的上下文中。让我们来看两个例子,eval 和立即执行函数表达式: ...
Let's look at an example of how you may do this: function Animal(name) { this.name = name; } Animal.prototype.age=1; function Cat(name, color) { Animal.call(this, name); this.color = color; } Cat.prototype = new Animal(null); var catC = new Cat("Fluffy", "White"); catC....
Leaflet|©OpenStreetMapcontributors Here we create a map in the'map'div, addtiles of our choice, and then add a marker with some text in a popup: varmap = L.map('map').setView([51.505, -0.09],13); L.tileLayer('https://tile.openstreetmap.org/{z}/{x}/{y}.png', { attribut...
the open dialog, continue.// When we hit the save dialog, break.if(host.memory.readWideString(address) =="Open") {// host.diagnostics.debugLog("We're opening, let's continue!\n");ctl.ExecuteCommand("gc"); }else{//host.diagnostics.debugLog("We're saving, let's break!\n");} }...