tl;dr: NaN is treated differently: [NaN].indexOf(NaN) > -1 is false [NaN].includes(NaN) is true From the proposal: Motivation When using ECMAScript arrays, it is commonly desired to determine if the array includes an element. The prevailing pattern for this is if (arr.indexOf(el) !== -1) { … } with various other possibilities, e.g. arr.indexOf(el) >= 0, or … Read more
You have to pass a promise to await. Convert the observable’s next event to a promise and await that. if (condition) { await observable.first().toPromise(); } Edit note: This answer originally used .take(1) but was changed to use .first() which avoids the issue of the Promise never resolving if the stream ends before a value comes … Read more
According to the MDN reference page, includes is not supported on Internet Explorer. The simplest alternative is to use indexOf, like this: if(window.location.hash.indexOf(“?”) >= 0) { … }
If you use Babel you can use the following syntax to copy property b from x into variable b and then copy rest of properties into variable y: let x = {a: 1, b: 2, c: 3, z:26}; let {b, …y} = x; and it will be transpiled into: “use strict”; function _objectWithoutProperties(obj, keys) { … Read more