Javascript overwrite destructured let variable

Question

Problem

Is it possible to overwrite multiple variables assigned with let

const somefunction = (data) => ({a:1+data, b:2-data, c: 2*data, d: 3+1*data})

let {a, b, c, d} = somefunction(3)

Now, how can one overwrite {a, b, c, d} in one statement after calling someFunction with a different argument?

Possible Solutions

Not working! (obviously)

const somefunction = (data) => ({a:1+data, b:2-data, c: 2*data, d: 3+1*data})

let {a, b, c, d} = somefunction(3)
{a, b, c, d} = somefunction(5)

Working

This seems to work, but my prettier will remove the leading semicolon (+ the syntax is crazy)

const somefunction = (data) => ({a:1+data, b:2-data, c: 2*data, d: 3+1*data})

let {a, b, c, d} = somefunction(3)
;({a, b, c, d} = somefunction(5))

are there other ways?

You need to wrap {} in () in an arrow function that has no brackets for grouping statements: `const somefunction = data => ({a:1+data, b:2-data, c: 2*data, d: 3+1*data})` — mplungjan, Jun 19 '20 at 11:35
Adding the semicolon and wrapping `()` is the [only way](https://stackoverflow.com/questions/27386234/). You need to change prettier settings. — adiga, Jun 19 '20 at 11:35
add manually an semicolon `let {a, b, c, d} = somefunction(3);` — bill.gates, Jun 19 '20 at 11:36

mplungjan · Accepted Answer · 2020-06-19T11:47:11.723

7

You need to wrap {} in () in an arrow function that has no brackets for grouping statements:

const somefunction = data => ({a:1+data, b:2-data, c: 2*data, d: 3+1*data});

const {a,b,c,d} = somefunction(3)
console.log(a,b,c,d)

Or use {} and return

const somefunction = data => {
  return {a:1+data, b:2-data, c: 2*data, d: 3+1*data}
};

const {a,b,c,d} = somefunction(3)
console.log(a,b,c,d)

Overwrite using let:

const somefunction = data => ({a:1+data, b:2-data, c: 2*data, d: 3+1*data});

let {a,b,c,d} = somefunction(3);
console.log(a,b,c,d);

({a,b,c,d} = somefunction(5));

console.log(a,b,c,d);

Overwrite using var ( I wouldn't ;) )

const somefunction = data => ({a:1+data, b:2-data, c: 2*data, d: 3+1*data});

var {a,b,c,d} = somefunction(3);
console.log(a,b,c,d);

var {a,b,c,d} = somefunction(5);

console.log(a,b,c,d);

edited Jun 19 '20 at 11:47

answered Jun 19 '20 at 11:39

mplungjan

169,008
28
173
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1

Ahh I see, had a typo oin the first formula. See here: https://jsfiddle.net/hfqg2oLa/ – Fabian Bosler Jun 19 '20 at 11:40
1

Perhaps we are not talking about the same thing? – mplungjan Jun 19 '20 at 11:41
Jupp, you are right. had a typo in the first formula. However, the question is about overwriting all the variables in one go. – Fabian Bosler Jun 19 '20 at 11:42

score 1 · Answer 2 · answered Jun 19 '20 at 11:42

1

It's ugly, but you can use var instead of let.

const somefunction = (data) => {return {a:1+data, b:2-data, c: 2*data, d: 3+1*data}}

var {a, b, c, d} = somefunction(3)

console.log(a,b,c,d)

var {a, b, c, d} = somefunction(4)

console.log(a,b,c,d)

answered Jun 19 '20 at 11:42

Moritz Roessler

8,542
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That is most certainly a solution. I was under the impression not to use var anymore. What are the drawbacks? – Fabian Bosler Jun 19 '20 at 11:43
2

@FabianBosler The only drawback is that your declaration will be [hoisted](https://developer.mozilla.org/en-US/docs/Glossary/Hoisting) and it won't be block scoped. – Moritz Roessler Jun 19 '20 at 11:44

Javascript overwrite destructured let variable

Problem

Possible Solutions

Not working! (obviously)

Working

2 Answers2