log(array); // [ { "name": "a", "value": 1 }, { "name": "b", "value": 2 } ] const map = new Map().set('a', 1).set('b', 2); // 自定义 map 函数 const array = Array.from(map, ([name, value]) => value); console.log(array); // [1, 2] const map = ...
在下面的示例中,内置 JavaScript 方法用作回调函数。 // Apply Math.sqrt(value) to each element in an array. var numbers = [9, 16]; var result = numbers.map(Math.sqrt); document.write(result); // Output: 3,4 示例 map 方法可应用于一个字符串。 下面的示例阐释了这一点。
Here,arris an array. map() Parameters Themap()method takes in: callback- The function called for every array element. Its return values are added to the new array. It takes in: currentValue- The current element being passed from the array. thisArg(optional) - Value to use asthiswhen ex...
常规JavaScript对象的键必须是String或Symbol,下面的对象说明的这一点: const symbol = Symbol(); const string2 = 'string2'; const regularObject = { string1: 'value1', [string2]: 'value2', [symbol]: 'value3' }; 相比之下,Map允许你使用函数、对象和其它简单的类型(包括NaN)作为键,如下代码:...
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You can create a map by passing an array to thenew Map()constructor: Example // Create a Map constfruits =newMap([ ["apples",500], ["bananas",300], ["oranges",200] ]); Try it Yourself » Map.get() You get the value of a key in a map with theget()method ...
javascript基础1,主要写(==和 的区别), Array对象, Object对象, this关键字,短路操作,Set集合,Map集合和String字符串操作。 1. == , 1. 在js中需要值相等类型相等 2. == 在js中值相等,类型不相等会自动转换 2.Array 全部Array
To convert an array of objects into a map in JavaScript, you can utilize theArray.map()method toiteratethrough the array elements and create an array of key-value pairs. Subsequently, you can pass this array of key-value pairs to theMap()constructor tocreateaMapobject. ...
TheMap.set()method adds or updates an entry in aMapwith the specified key and value. The method takes thekeyandvaluethat should be added to theMapas parameters. #Convert a two-dimensional array to a Map in JavaScript Use theMap()constructor to convert a two-dimensional array to aMapobject...
Using map to reformat objects in an array Copy let kvArray = [{key: 1, value: 10}, {key: 2, value: 20}, /*from ww w . java2 s . c om*/ {key: 3, value: 30}] let reformattedArray = kvArray.map(obj => { let rObj = {}; rObj[obj.key] = obj.value+1; return ...