"Destructuring allows you to bind a set of variables to a corresponding set of values anywhere that you can normally bind a value to a single variable" ("Common Lisp the Language").
Questions tagged [destructuring]
1338 questions
13
votes
1 answer
Is this a bug in Method#to_proc? (Ruby 1.8.7)
Given the following method that takes one argument:
def foo(arg); p arg; end
I can call it with an empty array:
foo([])
# prints []
I can also save it as a Method object and call that with an empty array, with the same…
Sam Stokes
- 14,617
- 7
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- 33
13
votes
3 answers
Destructuring assignment in function call while preserving the object
Is there a way to do something like the following?
f = (o:{a:x}) {
console.log(o);
console.log(x);
}
f({a:0});
//Should Print:
//{a:0}
//0
To get the same result as the this.
f = function(o) {
var {a:x} = o;
console.log(o);
…
Diasiare
- 745
- 1
- 6
- 18
13
votes
3 answers
How to handle nested default parameters with object destructuring?
I am trying to figure out if it is possible to handle multiple levels of default parameters with destructuring. Since it is not easy to explain with words, here is a step-by-step example...
1 - Flat object destructuring with default…
Badacadabra
- 8,043
- 7
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- 49
13
votes
1 answer
Unpack array argument directly to parameters?
I know I can do this:
function (value: [boolean, string]) {
const [boolValue, stringValue] = value;
// make use of boolValue and stringValue
}
But am I able to do something like this?
// doesn't work
function ([boolValue: boolean,…
Dave Cousineau
- 12,154
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12
votes
1 answer
TS will not infer possible undefined when destructuring empty array
When looking at the inferred type of destructured element, it will assume the array is never empty.
const x: number[] = [];
const [first] = x; // first inferred as number
console.log(first); // undefined
if (first !== undefined) {
//…
EcksDy
- 1,289
- 9
- 25
12
votes
2 answers
Can the props in a destructuring assignment be transformed in place?
This works…
const { prop1:val1, prop2:val2 ) = req.query
val1 = val1.toLowerCase()
Though, I'm more inclined to do something like
const { prop1.toLowerCase():val1, prop2:val2 } = req.query
or
const { prop1:val1.toLowerCase(), prop2:val2 } =…
tjfwalker
- 494
- 3
- 18
12
votes
1 answer
Nested object destructuring and renaming
Is it possible to rename a variable when destructuring a nested object in JavaScript? Consider the following code:
const obj = {a: 2, b: {c: 3}};
const {a: A, b:{c}} = obj;
How can I rename c in above code like I renamed a to A?
const {a: A, b:{c}:…
darKnight
- 5,651
- 13
- 47
- 87
12
votes
3 answers
React-native animated.event custom onScroll listener
In official react-native documentation there is a section about Animated.event method. As example they use following code:
onScroll={Animated.event(
// scrollX = e.nativeEvent.contentOffset.x
[{ nativeEvent: {
contentOffset: {
…
Michal
- 4,952
- 8
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- 63
12
votes
3 answers
Destructuring nested objects as function parameters
In ES6 we can do:
let myFunc = ({name}) => {
console.log(name)
}
myFunc({name:'fred'}) // => logs 'fred'
But how do I do it for nested properties like this:
myFunc({event:{target:{name:'fred'}}}) // => I want it to log 'fred'
What should myFunc…
danday74
- 52,471
- 49
- 232
- 283
12
votes
2 answers
Method parameter: destructuring + keeping original parameter (ReactJS component)
is there any way to achieve method parameter destructuring, but also be able to get method parameter.
In the context of a React application with stateless components, I'd like to be able to replace
const MyComponent = (props) => {
const {prop1,…
Sebastien Lorber
- 89,644
- 67
- 288
- 419
12
votes
2 answers
How to use destructuring assignment to define enumerations in ES6?
You can use destructuring assignment to define enumerations in ES6 as follows:
var [red, green, blue] = [0, 1, 2];
Instead, I'd like the right hand side of the destructuring assignment to be dynamic. For example:
var MAX_ENUM_SIZE = 32;
var ENUM =…
Aadit M Shah
- 72,912
- 30
- 168
- 299
12
votes
1 answer
How to destructure option argument with all default values in ES6?
I use ES6 features with babel compiler.
I have a function which takes option object as an argument:
function myFunction({ option1 = true, option2 = 'whatever' }) {
console.log(option1, option2);
// do something...
}
When I call it,…
madox2
- 49,493
- 17
- 99
- 99
12
votes
1 answer
Where can I get info on the object parameter syntax for JavaScript functions?
If I want to call a function like this:
moo({ a: 4 });
Normally I'd have to phrase my function definition like this:
function moo(myArgObj) {
print(myArgObj.a);
}
But this awesome syntax is totally valid in spidermonkey for defining…
Verdagon
- 2,456
- 3
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11
votes
4 answers
Is it possible to destructure an object into existing variables?
I am trying to extract variables using object destructuring but those variables already exist, something like this
const x=1, y=2 // Those should be 1 and 2
const {x,y} = complexPoint
const point = {x,y}
Is there any way to do this without renaming…
Juan Caicedo
- 1,425
- 18
- 31
11
votes
1 answer
In ES6 is destructuring Class Instance properties permitted?
Suppose I have the following code:
class Foo {
constructor() {
this.a = 1;
this.b = 'something';
}
someMethod() {
// Is this legal?
let { a, b } = this;
}
}
Is the destructuring assignment in…
baseten
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