ES6 style getters are defined on the prototype, not on each individual person. To set the greeting property to enumerable you need to change: // Make enumerable (doesn’t work) Object.defineProperty(Person, ‘greeting’, {enumerable: true}); To: // Make enumerable Object.defineProperty(Person.prototype, ‘greeting’, {enumerable: true}); Object.keys only returns that object’s own enumerable properties, so properties on the prototype are … Read more
You can achieve it with a form of destructuring: const user = { _id: 1234, firstName: ‘John’, lastName: ‘Smith’ }; const { _id, …newUser } = user; console.debug(newUser); However, at the time of writing this answer, the spread (…) syntax is still at the ECMAScript proposal stage (stage 3), so it may not be universally … Read more
Jest describe.each expects an array of arrays in the first parameter. If you pass in a 1D array, internally it will be mapped to an array of arrays (i.e. passing [1, 2, 3] as first parameter would be converted to [[1], [2], [3]]). Each one of the arrays inside of the array is used as … Read more
You can use Array#reduce to make a counter lookup table based on the id key, then use Array#filter to remove any items that appeared only once in the lookup table. Time complexity is O(n). const values = [{id: 10, name: ‘someName1’}, {id: 10, name: ‘someName2′}, {id: 11, name:’someName3’}, {id: 12, name: ‘someName4’}]; const lookup = … Read more
It can be a Jest configuration issue. I solved forcing “node” as jest environment in package.json: “jest”: { “testEnvironment”: “node” } see docs: https://facebook.github.io/jest/docs/configuration.html#testenvironment-string
New webpack-dev-server is released, and it supports writeToDisk option. devServer: { writeToDisk: true }
Best you can get is github: GoogleChrome/proxy-polyfill According to Babel docs: Due to the limitations of ES5, Proxies cannot be transpiled or polyfilled.
There’s no formal ES6/JS extension, although majority of people seem to prefer .js. ECMAScript specific suffixes aren’t common. Mozilla is using two extensions within Firefox and FirefoxOS: .js and .jsm. No ECMA Script specific suffixes. For Gecko (the layout engine written largely in JS), they use both .js and .jsm. Example: one of the DOM … Read more
There is not, you could write a wrapper to do that. Object.freeze locks an object’s properties, but while Map instances are objects, the values they store are not properties, so freezing has no effect on them, just like any other class that has internal state hidden away. In a real ES6 environment where extending builtins … Read more
You could use Array.from() instead: Thanks to Pranav C Balan in the comments for the suggestion on further improving this. let m = Array.from({length: 6}, e => Array(12).fill(0)); m[0][0] = 1; console.log(m[0][0]); // Expecting 1 console.log(m[0][1]); // Expecting 0 console.log(m[1][0]); // Expecting 0 Original Statement (Better optimized above): let m = Array.from({length: 6}, e => … Read more