Syntax operator for "default assignment if value doesn't exits"

Rob Ede robjtede at icloud.com
Sat Jan 12 14:54:19 UTC 2019


pretty succinct with existing de-structuring syntax:

```
const [variable = defaultValue] =  [maybeUndefinedValue]

const fn = ({ key = defaultValue }) => {  console.log(key); }
```

> On 11 Jan 2019, at 12:00, es-discuss-request at mozilla.org wrote:
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> Today's Topics:
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>   1. Syntax operator for "default assignment if value doesn't
>      exits" (Sultan)
> 
> From: Sultan <thysultan at gmail.com>
> Subject: Syntax operator for "default assignment if value doesn't exits"
> Date: 11 January 2019 at 10:52:12 GMT
> To: es-discuss <es-discuss at mozilla.org>
> 
> 
> An operator syntax for the the "typeof" pattern used to detect if a environment/object has a value:
> 
> if (typeof variable === 'undefined') {...}
> if (typeof object.key === 'undefined') {...}
> 
> This could manifest in destructuring as the following
> 
> var fn = ({ key ||= 1 }) => {
> }
> 
> And with variables as:
> 
> var global ||= {}
> 
> Equivalent code:
> 
> (arg) => {
>     if (typeof arg.key === 'undefined') {
>         arg.key = 1
>     }
> }
> 
> if (typeof global === 'undefined') {
> var global = {}
> }
> 
> 
> 
> 
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