arrow-functions

问题 How can I filler the below array on common id and output should have unique and latest history number const input = [{ "id": 134116, "user": "admin", "historyno": "134116-0" }, { "id": 134132, "user": "admin", "historyno": "134132-0" }, { "id": 134132, "user": "admin", "historyno": "134132-1" }, { "id": 134133, "user": "admin", "historyno": "134133-0" }, { "id": 134133, "user": "admin", "historyno": "134133-1" }]; let output = []; let tempId; for (let i = 0; i < input.length; i++) { if (input

问题 Kind of a sequel to this question, I need to accept multiple objects in a POST request and then for each object process it, save it, and then return the saved object to the frontend (so that the client can see which columns were successfully edited). When I use .map, it does save to the database and I can confirm this. However, I have two problems: It does not execute res.locals.retval.addData(dtoObject); correctly, and my returning payload has no data transfer objects inside of it. My object

问题 Kind of a sequel to this question, I need to accept multiple objects in a POST request and then for each object process it, save it, and then return the saved object to the frontend (so that the client can see which columns were successfully edited). When I use .map, it does save to the database and I can confirm this. However, I have two problems: It does not execute res.locals.retval.addData(dtoObject); correctly, and my returning payload has no data transfer objects inside of it. My object

问题 This question already has answers here : How does the “this” keyword work? (22 answers) Closed 3 years ago . I very confusing about the value of this at the moment of an invocation function using arrow functions. Let's take my example: var obj = { property: 5, func1: function () { console.log(this.property); }, func2: () => { console.log(this.property); } } When i put this code on the browser console, an interesting thing happens, func1() will output 5 as expected *, but when i run func2 i

问题 I'm using arrow functions and I'm debugging with Chrome and Firefox Dev Tool. I am getting, this as undefined, even though the code still works. My assumption is, that it has something to do with source-maps. Here are the tools I use in order to build the my code: webpack (devtool: eval) babel-loader (es5 preset) typescript-loader 回答1: The problem is that the chrome debugger believes that the this in the source code refers to the run-time this , but this inside a arrow function in typescript

问题 I saw this line of code in a correction in a coding game const tC = readline().split(' ').map(x => +x); I wonder what it does because when I log this function it render the same thing that this one const tC = readline().split(' ').map(x => x); but the rest of the code didn't work Context : /** Temperatures (easy) https://www.codingame.com/training/easy/temperatures * Solving this puzzle validates that the loop concept is understood and that * you can compare a list of values. * This puzzle is

问题 As mention in document https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Functions/Arrow_functions Arrow functions do not have prototype property but when I run this on fiddle, why does it gives an object ? http://es6console.com/iwyii5vm/ Why it is giving a object? var Foo = () => {}; console.log(Foo.prototype); 回答1: If you run this code in a native ES6 engine, there will not be a prototype property for arrow functions. Example of native ES6: var Foo = () => {}; console.log(Foo

问题 I have that code: function defineProperty(object, name, callback){ if(object.prototype){ Object.defineProperty(object.prototype, name, {"get": callback}); } } defineProperty(String, "isEmpty", function(){return this.length === 0;}); and I use it as below: console.log("".isEmpty, "abc".isEmpty); and it returns: true, false Now, I would like to change function to something like this: defineProperty(String, "isEmptyWithArrow", () => this.length === 0); but "this" refers to Window and I do not

问题 I am running a React project using npm. After hours of research and experimenting, everywhere says I have to add the following code to my ".babelrc" file, which I do not have in my directory and cannot create: { "plugins": [ ["@babel/plugin-proposal-class-properties", { "loose": true }] ] } But this leads to the following error when I run the code: ERROR in ./src/components/NavBar/Menu.js Module build failed (from ./node_modules/babel-loader/lib/index.js): SyntaxError: /Users/ymoondhra

问题 I'm using react-native and react-relay, therefore I've the following .babelrc file: { "sourceMaps": "both", "presets": [ "./plugins/babelRelayPlugin", "react-native" ], "passPerPreset": true } Adding a dependency which uses arrow functions in their components as the MKIconToggle from react-native-material-kit (https://github.com/xinthink/react-native-material-kit) doesn't get transpiled correctly and the this reference is lost/wrong. The original code which ultimately causes the error looks