es6-map

问题 If I have a sample data that looks like this I need to get finalResult array from result array: let result = [{ type: ['Science'], link: "www.educatorsector.com" }, { type: ['Sports', 'News'], link: "www.skysports-news.com" }, { type: ['Sports', 'Science'], link: "www.cnn-news.com" }]; finalResult = [ { type : "Science", numberOfLinks : 2 }, { type : "Sports", numberOfLinks : 2 }, { type : "News", numberOfLinks : 1 }] orThisFinalResult = [ { type : "Science", links : ["www.educatorsector.com"

问题 If I have a sample data that looks like this I need to get finalResult array from result array: let result = [{ type: ['Science'], link: "www.educatorsector.com" }, { type: ['Sports', 'News'], link: "www.skysports-news.com" }, { type: ['Sports', 'Science'], link: "www.cnn-news.com" }]; finalResult = [ { type : "Science", numberOfLinks : 2 }, { type : "Sports", numberOfLinks : 2 }, { type : "News", numberOfLinks : 1 }] orThisFinalResult = [ { type : "Science", links : ["www.educatorsector.com"

问题 If I have a sample data that looks like this I need to get finalResult array from result array: let result = [{ type: ['Science'], link: "www.educatorsector.com" }, { type: ['Sports', 'News'], link: "www.skysports-news.com" }, { type: ['Sports', 'Science'], link: "www.cnn-news.com" }]; finalResult = [ { type : "Science", numberOfLinks : 2 }, { type : "Sports", numberOfLinks : 2 }, { type : "News", numberOfLinks : 1 }] orThisFinalResult = [ { type : "Science", links : ["www.educatorsector.com"

问题 I have the map posted below in the code section. I added some values to the map as shown.But when i tried to display the contents of the map using 'getOwnPropertyNames' as shown in th code, the log statement in the loop does not display any thing. please let me know how to utilize 'getOwnPropertyNames' properly code : const mymap = new Map(); const mapKeyToValue = (key, value) => { mymap.set(key, value); }; const getMyMap = () => mymap; mapKeyToValue('1', [{ 'a': 10, 'b': 100, 'c': 1000 }]);

问题 I have an array of objects, where each object has a unique member called id . How do I create a Map where the id if the Map's key? 回答1: You want to reduce your array into a map: const arr = [{id:1},{id:2},{id:2}]; const map = arr.reduce((acc, item) => acc.set(item.id, item), new Map()); console.log(map.get(1)); Here is a JSPref against using map and forEach . In Chrome v53 reduce is fastest, then forEach with map being the slowest. 回答2: You can use Array.prototype.map() to map the array

问题 I have an array of objects, where each object has a unique member called id . How do I create a Map where the id if the Map's key? 回答1: You want to reduce your array into a map: const arr = [{id:1},{id:2},{id:2}]; const map = arr.reduce((acc, item) => acc.set(item.id, item), new Map()); console.log(map.get(1)); Here is a JSPref against using map and forEach . In Chrome v53 reduce is fastest, then forEach with map being the slowest. 回答2: You can use Array.prototype.map() to map the array

问题 I'm getting the following error even when I run node with high heap memory using the following command: node --max-old-space-size=8000 manipulateFiles.js FATAL ERROR: invalid table size Allocation failed - JavaScript heap out of memory 1: 0x8dc510 node::Abort() [node] 2: 0x8dc55c [node] 3: 0xad9b5e v8::Utils::ReportOOMFailure(v8::internal::Isolate*, char const*, bool) [node] 4: 0xad9d94 v8::internal::V8::FatalProcessOutOfMemory(v8::internal::Isolate*, char const*, bool) [node] 5: 0xec7bf2

问题 I have this Express route: app.use('/stop_jobs', function (req, res, next) { const jobId = req.query && req.query.job_id; const stopped : Array<any> = []; for (let j of runningJobs.keys()) { if(j.id === jobId){ stopped.push(j.stopThisInstance()); } } res.json({success: {stopped}}); }); where const runningJobs = new Map<CDTChronBase,CDTChronBase>(); (CDTChronBase is a class) the above works, but I'd like to simplify it if possible, something like this: app.use('/stop_jobs', function (req, res,

问题 With Array, I can use array[index]++ But with Map, I only know map.set(index,map.get(index)+1) I think it looks bad, and if index is a long name function, I have to split it into two lines. Is there a more concise way to implement map[index]++ 回答1: I could only suggest a helper function, like function update(map, key, fn) { return map.set(key, fn(map.get(key), key)); } update(table, index, i=>i+1); There is no syntactic sugar for assignments, and therefore no shorthand assignments either. If

问题 How to show No Result message when the search result is empty with in map() ? export class Properties extends React.Component { render () { const { data, searchText } = this.props; const offersList = data .filter(offerDetail => { return offerDetail.city.toLowerCase().indexOf(searchText.toLowerCase()) >= 0; }) .map(offerDetail => { return ( <div className="offer" key={offerDetail.id}> <h2 className="offer-title">{offerDetail.title}</h2> <p className="offer-location"><i className="location-icon