js switch(true){caseisSquare(shape):console.log("该形状是一个正方形。");// 失败,因为正方形也是矩形的一种!caseisRectangle(shape):console.log("该形状是一个矩形。");caseisQuadrilateral(shape):console.log("该形状是一个四边形。");break;caseisCircle(shape):console.log("该形状是一个圆形。")...
jsCopy to Clipboard console.log(square(5)); // 25 function square(n) { return n * n; } 尽管square() 函数在声明之前被调用,但此代码的运行并没有任何错误。这是因为 JavaScript 解释器会将整个函数声明提升到当前作用域的顶部,因此上面的代码等价于: jsCopy to Clipboard // 所有函数声明实际上都位...
In JavaScript, everything is an object. An object is a collection of related functionality stored in a single grouping. You can create your own objects, but that is quite advanced. The built-in objects that your browser contains allow you to do lots of useful things. For example, we first...
jsCopy to Clipboard console.log(typeof getThisStrict()); // "undefined" 在非严格模式下,一个特殊的过程称为 this 替换确保this 的值总是一个对象。这意味着:如果一个函数被调用时 this 被设置为 undefined 或null,this 会被替换为 globalThis。 如果函数被调用时 this 被设置为一个原始值,this 会被...
switch 语句和 export 语句页面. 例子 在switch语句中使用default In the following example, if expr evaluates to "Bananas" or "Apples", the program matches the values with either the case "Bananas" or "Apples" and executes the corresponding statement. The default keyword will help in any other ...
JavaScript 設計成簡單的物件樣式。一個物件是一些屬性的集合,而屬性是鍵與值之間的關聯。一個屬性能夠是一個函數 (Function),也叫做方法 (Method)。此外,物件是瀏覽器預定義的,你也可以定義你自己的物件。
files Remove Noah from switch statement example (mdn#3833) Apr 5, 2021 pr-lint PR hygiene checking (mdn#910) Feb 4, 2021 rfcs add rfc for modernizing learn js (mdn#3530) Apr 1, 2021 scripts up-to-date check script (mdn#1095) Jan 13, 2021 .editorconfig chore: Add initial EditorConfig...
or in javascript: ```js function intersect(sphere, other) { // we are using multiplications because it's faster than calling math.pow - const distance = math.sqrt((sphere.x - other.x) * (sphere.x - other.x) + - (sphere.y - other.y) * (sphere.y - other.y) + - (sphere.z...
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 ...
Object.keys() 方法会返回一个由给定对象的所有可枚举自身属性的属性名组成的数组,数组中属性名的排列顺序和使用for-in循环遍历该对象时返回的顺序一致(两者的主要区别是 for-in 还会遍历出一个对象从其原型链上继承到的可枚举属性)。 209 Object.observe() ECMAScript7, Experimental, Expérimental, JavaScript, ...