spread-syntax

TypeScript 2.8.3 Type must have a Symbol.iterator method that returns an iterator

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this has helped me. in tsconfig, add this : { “compilerOptions”: { “lib”: [ “es5”, “es6”, “dom”, “dom.iterable” ] } } This is required for tsconfig to know which interfaces to import while transpiling your code. dom.iterable includes all the interfaces mentioned here : https://github.com/microsoft/TypeScript/blob/master/lib/lib.dom.iterable.d.ts Also thanks to @domlas for mentioning this. I already upvoted … Read more

Replace array entry with spread syntax in one line of code? [duplicate]

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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.

Is there an Object spread syntax in python 2.7x like in Javascript?

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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

What is SpreadElement in ECMAScript documentation? Is it the same as Spread syntax at MDN?

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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

Spreading undefined in array vs object

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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

Spread Syntax vs Rest Parameter in ES2015 / ES6

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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