function map(f, a) { const result = new Array(a.length); for (let i = 0; i < a.length; i++) { result[i] = f(a[i]); } return result; } 在以下代码中,该函数接收由函数表达式定义的函数,并对作为第二个参数接收的数组的每个元素执行该函数: jsCopy to Clipboard function map(f,...
MimeTypeArray.length Deprecated The number of items in the array.Instance methods MimeTypeArray.item() Deprecated Returns the MimeType object with the specified index. MimeTypeArray.namedItem() Deprecated Returns the MimeType object with the specified name.Example The following example tests wheth...
$ mdn array#Methods Opens theArraydocumentation on MDN in your browser and jumps down to theMethodssection. Compatability mdnusesopenwhich tries to find a suitable command for opening URLs in your browser, regardless of which platform you're on. If you're having problems usingmdnon your platfo...
jsCopy to Clipboard function init() { var name = "Mozilla"; // name 是 init 创建的局部变量 function displayName() { // displayName() 是内部函数,它创建了一个闭包 console.log(name); // 使用在父函数中声明的变量 } displayName(); } init(); init() 创建了一个名为 name 的局部变量和...
When you create a string, your variable becomes a string object instance, and as a result has a large number ofproperties(即.XXX)andmethods(即.XXX())available to it. 您可以使用方括号符号返回字符串中的字符。 属性length:获取字符串或数组的长度。
There's also no option to pass a thisArg to setTimeout as there is in Array methods such as forEach() and reduce(). As shown below, using call to set this doesn't work either.jsCopy to Clipboard setTimeout.call(myArray, myArray.myMethod, 2.0 * 1000); // error setTimeout.call...
Once established, you can reference elements in the array using the object's methods, or using standard array index syntax (that is, using bracket notation). 311 WeakMap WeakMap对象就是简单的键/值映射.但键只能是对象值,不可以是原始值. 312 WeakMap.prototype.delete() delete() 方法可以从...
jsCopy to Clipboard // Legacy array comprehensions [for (x of iterable) x] [for (x of iterable) if (condition) x] [for (x of iterable) for (y of iterable) x + y] // Legacy generator comprehensions (for (x of iterable) x) (for (x of iterable) if (condition) x) (for (x ...
Learn about the Window interface, including its properties and methods, specifications and browser compatibility.
HTML #dom-settimeout-dev See also Polyfill ofsetTimeoutwhich allows passing arguments to the callback incore-js Window.clearTimeout() WorkerGlobalScope.setTimeout() Window.setInterval() Window.requestAnimationFrame() Window.queueMicrotask()...