Javascript arrow function unexpected token on if condition

Question

Can somebody tell me please what is wrong with this arrow function. It throws me an error

unexpected token on begin of if condition

selected_devices
  .map( device => if( device.device_id === device_id ) device.source = 'included' )

You need {} when you have an if or other things that are not a single statement - also do NOT use map if you want forEach — mplungjan, Mar 02 '22 at 08:37
Perhaps you meant `selected_devices.forEach( device => device.source = device.device_id === device_id ? 'included' : device.source)` — mplungjan, Mar 02 '22 at 08:40
@mplungjan Why should I not to use map()? Dont understand it. — Čamo, Mar 02 '22 at 08:42

mplungjan · Accepted Answer · 2022-03-02T08:43:48.480

2

You need {} when you have an if or other things that are not a single statement - also do NOT use map if you want forEach since map creates an unnecessary array you then throw away

selected_devices
  .forEach(device => device.source = device.device_id === device_id  ? 'included' : device.source)

or perhaps

selected_devices
  .filter( device => device.device_id === device_id)
  .forEach(device => device.source = 'included')

edited Mar 02 '22 at 08:43

answered Mar 02 '22 at 08:42

mplungjan

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Can you tell me why not map? – Čamo Mar 02 '22 at 08:43
1

Map creates an unnecessary array you then throw away – mplungjan Mar 02 '22 at 08:43

フィン · Answer 2 · 2022-03-02T08:39:07.970

0

looks like you forgot to add brackets like this

selected_devices.map((device) => {
   if (device.device_id === device_id) device.source = 
   'included'
   return device
})

But you can also do with the ternary operator like this

selected_devices.map((device) =>
   device.device_id === device_id ? { ...device, device.source: 
   'included' } : device,
)

edited Mar 02 '22 at 08:39

answered Mar 02 '22 at 08:37

フィン

21
4

Brackets work with return, but it should not be necessary. – Čamo Mar 02 '22 at 08:40
@Čamo You need brackets if you want to use "if" because you can use if statements only in code blocks. If you don't want to use brackets and/or a return statement you can use the ternary operator. – フィン Mar 02 '22 at 08:43

Javascript arrow function unexpected token on if condition

2 Answers2