spread-syntax

来源： https://stackoverflow.com/questions/51519149/how-to-return-a-spread-operator-in-a-map-arrow-function-in-one-line

来源： https://stackoverflow.com/questions/64116014/how-to-access-the-nested-property-by-name-of-the-javascript-object-when-the-obje

问题 Is there any implementation in C# like JavaScript's spread syntax? var arr = new []{ "1", "2"//... }; Console.WriteLine(...arr); 回答1: There isn't a spread option. And there are reasons. Properties aren't an array in C# unless you use the params keyword Properties that use the param keyword would have to either: Share the same type Have a castable shared type such as double for numerics Be of type object[] (as object is the root type of everything) However, having said that, you can get

问题 I have code: let a = {a: 'a', b: 'b'}; let b = {c: 'c', d: 'd'}; let c = {...a, ...b}; In chrome / firefox /... its display: c = {a: 'a', b: 'b', c: 'c', d: 'd'} , but in microsoft edge its trow error Expected identifier, string or number . I try to use cdn.polyfill.io and https://babeljs.io/docs/en/babel-polyfill but no luck. What i can do to run my webpack code in microsoft edge ? 回答1: The { ...obj } syntax is called "Object Rest/Spread Properties" and it's a part of ECMAScript 2018 which

问题 Can someone explain me why const getabc = ()=> ({a:'aa',b:'bb',c:123}); let a, b, c; { a, b, c } = {...getabc()} this works and const getabc = ()=> ({a:'aa',b:'bb',c:123}); let a, b, c; { a, b, c } = {...getabc()}; this does not (note semicolon at the end) 回答1: This has nothing to do with spread syntax or semicolons. Object destructuring assignments that are not preceded with something like var , const , or let must use parentheses (or in some other way occur as a an expression within a

问题 Can someone explain me why const getabc = ()=> ({a:'aa',b:'bb',c:123}); let a, b, c; { a, b, c } = {...getabc()} this works and const getabc = ()=> ({a:'aa',b:'bb',c:123}); let a, b, c; { a, b, c } = {...getabc()}; this does not (note semicolon at the end) 回答1: This has nothing to do with spread syntax or semicolons. Object destructuring assignments that are not preceded with something like var , const , or let must use parentheses (or in some other way occur as a an expression within a

问题 DISCLAIMER: I'm not terribly familiar with webpack or babel outside of simple setup, so if the question isn't clear then I apologize and will do my best to offer further clarity. So, the situation currently is that a coworker updated a bunch of packages recently, babel among them, and babel is no longer transpiling the code properly for .forEach and spread operators in ie11 (specifically when iterating over a node list). The resulting behavior is a bit frustrating; simply put, nothing happens

问题 I have a nested array like this const names= [[{name: "John"}, {name: "Mary"}], [{name: "Paul"}, {name: "Peter"}]]; I would like inject country into the nested object const country = {country :"USA"} so that output looks like [{name: "John", country : "USA"}, {etc} ,{etc} ] The code idea have is something like this const combined = names.map((map)=> Object.assign({}, country, /*something to extract name from nested array names*/), {country} ) Any suggestions how i could spread the object in

问题 Whenever you want to use a computed getter with the mapGetter helper from Vuex you would use it like so: ...mapGetters([ 'getter1', 'getter2', 'etc' ]) I have seen the spread operator used before to expand arrays to be used as function arguments, but not in front of a method like we see here with the mapGetters example. I can't really find examples of this syntax either, when looking in mozilla documentation for example: https://developer.mozilla.org/nl/docs/Web/JavaScript/Reference/Operators

问题 I want to merge two typescript objects (using object spread): var one = { a: 1 } var two = { a: 2, b: 3 } var m = {...one, ...two} // problem as property `a` is overwritten I want to use the type system to ensure none of the properties in the second object overwrite any properties in the first. I am not sure why the following solution does not work: type UniqueObject<T extends {[K in keyof U]?: any}, U> = {[K in keyof U]: T[K] extends U[K] ? never : U[K]} var one = { a: 1 } var two1 = { a: 2,