The spread operator in the arrays RFC has been implemented in PHP 7.4: $ary = [3, 4, 5]; return [1, 2, …$ary]; // same as [1, 2, 3, 4, 5] Caveat: The unpacked array/Traversable can only have integer keys. For string keys array_merge() is still required.
This is object rest operator, it creates an object from all properties that weren’t explicitly destructured. Note: since object rest/spread is still a stage 3 proposal, and requires a babel transform to work. const obj = { a: 1, b: 2, c: 3}; const { a, …everythingElse } = obj; console.log(a); console.log(everythingElse); It’s equivalent to … Read more
There is no spread operator! This is quite important in order to understand what’s happening, so I have to start with it. There is no spread operator defined in the language. There is spread syntax but as a sub-category of other types of syntax. This sounds like just semantics but it has a very real … Read more
The properties are added in order, so if you want to override existing properties, you need to put them at the end instead of at the beginning: return { value: { …initialState, …newObject } } You don’t need newObject (unless you already have it lying around), though: return { value: { …initialState, isAvailable: newValue } … Read more
Is the difference between them is just syntax or there’s a performance issue? Both, and more… Rest parameters: Are a known idiom in other languages (Ruby, Python). Are esier to read and maintain (vs. slice). Are easier to understand for beginners. Can (and likely will) result in better performance, since engines can optimize. Are tool … Read more
As noted in the comments, and summarized by @ftor from #687, object spread is equivalent1 to Object.assign() (issues #687, #45), whereas spread in array literal context is iterable spread. Quoting Ecma-262 6.0, Object.assign() is defined as: 19.1.2.1 Object.assign ( target, …sources ) The assign function is used to copy the values of all of the … Read more
Why can’t spread operator be used multiple times? … is not an operator. (…arr) is not valid JavaScript. … is only allowed inside array literals and in arguments lists, but those are special forms of the syntax (notice the … in the production rules below). ArrayLiteral ArrayLiteral : [ Elision_opt ] [ ElementList ] [ … Read more
Circular type aliases are not really supported except in certain cases. (UPDATE TS 4.1, these are more supported now, but I’m still inclined to represent flow() as operating on AsChain that verifies a particular array of functions instead of trying to come up with a Chain that matches all valid arrays of functions) Instead of … 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);
When using spread, you are expanding a single variable into more: var abc = [‘a’, ‘b’, ‘c’]; var def = [‘d’, ‘e’, ‘f’]; var alpha = [ …abc, …def ]; console.log(alpha)// alpha == [‘a’, ‘b’, ‘c’, ‘d’, ‘e’, ‘f’]; When using rest arguments, you are collapsing all remaining arguments of a function into one array: … Read more