Detecting an "invalid date" Date instance in JavaScript
I'd like to tell the difference between valid and invalid date objects in JS, but couldn't figure out how: var d = new Date("foo"); console.log(d.toString()); // shows 'Invalid Date' console.log(typeof d); // shows 'object' console.log(d instanceof Date); // shows 'true' Any ideas for writing an isValidDate function? Ash recommended Date.parse for parsing date strings, which gives an authoritative
Is there a mechanism to loop x times in ES6 (ECMAScript 6) without mutable variables?
The typical way to loop x times in JavaScript is: for (var i = 0; i < x; i++) doStuff(i); But I don't want to use the ++ operator or have any mutable variables at all. So is there a way, in ES6, to loop x times another way? I love Ruby's mechanism: x.times do |i| do_stuff(i) end Anything similar in JavaScript/ES6? I could kind of cheat and make my own generator: function* times(x) { for (var i = 0
Most efficient method to groupby on an array of objects
What is the most efficient way to groupby objects in an array? For example, given this array of objects: [ { Phase: "Phase 1", Step: "Step 1", Task: "Task 1", Value: "5" }, { Phase: "Phase 1", Step: "Step 1", Task: "Task 2", Value: "10" }, { Phase: "Phase 1", Step: "Step 2", Task: "Task 1", Value: "15" }, { Phase: "Phase 1", Step: "Step 2", Task: "Task 2", Value: "20" }, { Phase: "Phase 2", Step:
Why Is `Export Default Const` invalid?
I see that the following is fine: const Tab = connect( mapState, mapDispatch )( Tabs ); export default Tab; However, this is incorrect: export default const Tab = connect( mapState, mapDispatch )( Tabs ); Yet this is fine: export default Tab = connect( mapState, mapDispatch )( Tabs ); Can this be explained please why const is invalid with export default? Is it an unnecessary addition & anything de
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