how to handle this default parameter in javascript?

Question

I have a function which has two default parameters and one regular parameter.

var Fields = function ($content, result = failedObject, job = true) 
{
    ...
}

When I call Fields($content,job), job here could be true or false, the result parameter takes in the job value rather than the third parameter. Works good in the case if Fields($content,result).

Any good way to tackle this situation.

What exactly is your question? – Tom O. Jul 18 '19 at 15:33 — Tom O., Jul 18 '19 at 15:33

score 2 · Answer 1 · answered Jul 18 '19 at 15:36

2

you would call Fields($content, undefined, job) to use the default value for the parameter result

answered Jul 18 '19 at 15:36

dikuw

1,134
13
22

zronn · Answer 2 · 2019-07-18T16:28:52.087

1

You could use a destructured argument :

var Fields = function ($content, { result = failedObject, job = true } = { }) {
    ...
}

Then, when you call the function :

const data = { result: anotherObject, job = false };
Fields('toto', data);

Or, in your specific case :

const data = { job = false };
Fields('toto', data); // result still is a failedObject

edited Jul 18 '19 at 16:28

answered Jul 18 '19 at 15:37

zronn

1,026
8
26

Downvoting, no comment ? – zronn Jul 18 '19 at 15:41
There is no need to change function signature. Just pass `undefined` as param value – ponury-kostek Jul 18 '19 at 15:45
What if OP can't change function signature? – ponury-kostek Jul 18 '19 at 15:46
@ponury-kostek I'm just suggesting a another possible solution, OP doesn't says he wants to keep the same signature – zronn Jul 18 '19 at 15:49
So why not to pass all parameters in single object? – ponury-kostek Jul 18 '19 at 15:51
Yes, this is another solution among many others – zronn Jul 18 '19 at 15:53

score 1 · Answer 3 · answered Jul 18 '19 at 15:37

1

if I understood your question correctly, javascript does not support named parameters natively, so you can call by Fields($content, undefined, job)

or using an object as parameter for your function instead of 3 params.

answered Jul 18 '19 at 15:37

IWHKYB

481
3
11

score 0 · Answer 4 · answered Jul 18 '19 at 15:35

0

Pass empty/undefined/null:

Fields($content, , job);

answered Jul 18 '19 at 15:35

Rob Wood

415
5
11

1

`Fields($content, , job)` is syntax error. Passing `null` will set param value to `null`. Only `undefined` is proper way. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Default_parameters#Passing_undefined_vs._other_falsy_values – ponury-kostek Jul 18 '19 at 15:43
yeah exactly only undefined would work . – Devuatprod Jul 18 '19 at 15:45

score -1 · Answer 5 · answered Jul 18 '19 at 15:37

-1

You must switch the order(like below), or using an array and treat inside function.

var Fields = function ($content, job = true, result = failedObject, ) 
     {
     }

answered Jul 18 '19 at 15:37

Ricardo CF

79
5

how to handle this default parameter in javascript?

5 Answers5