webidlCopy to Clipboard interface RTCStatsReport { readonly maplike<DOMString, object>; }; 类Map 对象可以是只读的,也可以是可写的(参见上面 IDL 中的 readonly 关键字)。 只读的类 Map 对象具有 size 属性,以及这些方法:entries()、forEach()、keys(
Array.prototype.map() numbersfilteredNumbersnumbersindexnum}});// index 从 0 开始,因此 filterNumbers 为 1、2、3 和 undefined。// filteredNumbers 是 [1, 2, 3, undefined]// numbers 依旧是 [1, 2, 3, 4] Specification ECMAScript® 2026 Language Specification...
Map 对象就是一个简单的键/值对映射集合,可以按照数据插入时的顺序遍历所有的元素。 下面的代码演示了使用 Map 进行的一些基本操作。请参考 Map 以获取更多的样例和完整的 API。你可以使用 for...of 循环来在每一次迭代中得到 [key, value] 数组。 jsCopy to Clipboard const sayings = new Map(); sayings...
Window.createImageBitmap() Accepts a variety of different image sources, and returns a Promise which resolves to an ImageBitmap. Optionally the source is cropped to the rectangle of pixels originating at (sx, sy) with width sw, and height sh. Window.dump() Non-standard Writes a message...
var elems = document.querySelectorAll('select option:checked'); var values = Array.prototype.map.call(elems, function(obj) { return obj.value; }); 反转字符串 var str = '12345'; Array.prototype.map.call(str, function(x) { return x; }).reverse().join(''); // Output: '54321' /...
core-js 中Array.prototype.filter 的polyfill 索引集合 Array Array.prototype.forEach() Array.prototype.every() Array.prototype.map() Array.prototype.some() Array.prototype.reduce() TypedArray.prototype.filter()Help improve MDN Was this page helpful to you? YesNoLearn how to contribute. This page...
console.log(ary2.next());//Object {value: Array[2], done: false} value:Array[2] ---[0:1,1:2]; //可以看出每次执行这个next().都会返回一个该数组的索引和值组成的新的数组,被包在一个对象的value属性里 //所以可以通过ary2.next().value获取当前的值和索引 3...
Theunshiftmethod inserts the given values to the beginning of an array-like object. unshiftis intentionally generic; this method can becalledorappliedto objects resembling arrays. Objects which do not contain alengthproperty reflecting the last in a series of consecutive, zero-based numerical properti...
2. 使用map let arrMap = [{ name: 'aaa', age: 23, address: 'henan' }, { name: 'bbbb', age: 26, address: 'hebei' }, { name: 'cccc', age: 27, address: 'anhui' }] arrMap = arrMap.map(obj => obj.name) console.log(arrMap) //打印结果:['aaa','bbb','ccc'] 3. 使...
2. 使用map let arrMap = [{ name: 'aaa', age: 23, address: 'henan' }, { name: 'bbbb', age: 26, address: 'hebei' }, { name: 'cccc', age: 27, address: 'anhui' }] arrMap = arrMap.map(obj => obj.name) console.log(arrMap) //打印结果:['aaa','bbb','ccc'] ...