This behavior is useful for doing something like optional spreading: function foo(options) { const bar = { baz: 1, …(options && options.bar) // options and bar can be undefined } } And it gets even better with optional chaining, which is in Stage 4 now (and already available in TypeScript 3.7+): function foo(options) { const … Read more
Q1: The simplicity of the reducer is a result of not having to search through the array to find the right entry. Not having to search through the array is the advantage. Selectors and other data accessors may and often do access these items by id. Having to search through the array for each access … Read more
Use JSON for deep copy var newObject = JSON.parse(JSON.stringify(oldObject)) var oldObject = { name: ‘A’, address: { street: ‘Station Road’, city: ‘Pune’ } } var newObject = JSON.parse(JSON.stringify(oldObject)); newObject.address.city = ‘Delhi’; console.log(‘newObject’); console.log(newObject); console.log(‘oldObject’); console.log(oldObject);
Update: With Typescript 2.3, you can now add “downlevelIteration”: true to your tsconfig, and this will work while targeting ES5. The downside of downlevelIteration is that TS will have to inject quite a bit of boilerplate when transpiling. The single line from the question transpiles with 21 lines of added boilerplate: (as of Typescript 2.6.1) … Read more
I know this is a bit of an old issue but the easiest solution in ES2015/ES6 I could come up with was actually quite simple, using Object.assign(), Hopefully this helps: /** * Simple object check. * @param item * @returns {boolean} */ export function isObject(item) { return (item && typeof item === ‘object’ && !Array.isArray(item)); … Read more
That’s property spread notation. It was added in ES2018 (spread for arrays/iterables was earlier, ES2015), but it’s been supported in React projects for a long time via transpilation (as “JSX spread attributes” even though you could do it elsewhere, too, not just attributes). {…this.props} spreads out the “own” enumerable properties in props as discrete properties … Read more