use Array.slice this.setState({ images: [ …this.state.images.slice(0, 4), updatedImage, …this.state.images.slice(5), ], }); Edit from original post: changed the 3 o a 4 in the second parameter of the slice method since the second parameter points to the member of the array that is beyond the last one kept, it now correctly answers the original question.
If you had Python >=3.5, you can use key-word expansion in dict literal: >>> d = {‘x’: ‘2’, ‘y’: ‘1’} >>> {**d, ‘x’:1} {‘x’: 1, ‘y’: ‘1’} This is sometimes referred to as “splatting”. If you are on Python 2.7, well, there is no equivalent. That’s the problem with using something that is over 7 … Read more
The term “spread operator” is kind of an “umbrella term” that refers to various syntactic constructs in ES6 which all look like …x. MDN does the same. However, this is misguiding, because … is not an operator (at least not in the sense the ECMAScript spec uses the term “operator”). It doesn’t generate a value … Read more
It’s not an operator. In all senses of the word, it’s not one. It has been a huge misconception since it was introduced and despite popular opinion — it’s not one, and there are a few objective points to be made: It doesn’t fit the definition of an operator It can’t be used as an … Read more
There isn’t a spread option. And there are reasons. Method Parameters aren’t an array in C# unless you use the params keyword Method Parameters that use the param keyword would have to either: Share the same type Have a castable shared type such as double for numerics Be of type object[] (as object is the … 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
Four dots actually have no meaning. … is the spread operator, and .0 is short for 0.0. Spreading 0 (or any number) into an object yields an empty object, therefore {}.
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
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