Possible to set default parameters as variable JS

Question

I'm writing my first ever jquery dependant plugin.

My question is can default parameters be variable like so:

var s = 400,
    m = 500,
    l = 700,
    xl = 960;

function breakpoints(s = s, m = m, l = l, xl = xl) {
  return {
    s: s,
    m: m,
    l: l,
    xl: xl
  };
};

When using console.log(s, m, l, xl); inside my initial breakpoints() declaration I get the error:

s is not defined

Thanks in advance for your help.

be on the look out for function hoisting.

Daniel A. White
– Daniel A. White

2017-08-31 13:00:01 +00:00
Commented Aug 31, 2017 at 13:00 — Daniel A. White
– Daniel A. White, Commented Aug 31, 2017 at 13:00
So it's just a typo?

Drag and Drop
– Drag and Drop

2017-08-31 13:02:43 +00:00
Commented Aug 31, 2017 at 13:02 — Drag and Drop
– Drag and Drop, Commented Aug 31, 2017 at 13:02

Rory McCrossan · Accepted Answer · 2017-08-31 13:01:21Z

5

ES6/ES2015 support default values on arguments, so your code will work so long as the browser supports those standards.

That being said you need to give the outer/inner variables different names, otherwise they won't be available where you attempt to use them. Try this:

var s = 400,
    m = 500,
    l = 700,
    xl = 960;

function breakpoints(_s = s, _m = m, _l = l, _xl = xl) {
  return {
    s: _s,
    m: _m,
    l: _l,
    xl: _xl
  };
};

console.log(breakpoints());

answered Aug 31, 2017 at 13:01

Rory McCrossan

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6 Comments

Duncan Thacker Over a year ago

Duplicating variable names in different scopes is a bit of an anti-pattern - I recommend using something like eslint to help flag it up.

DanMad Over a year ago

This answers my question @Rory. Will accept when I can. Thank you.

Rory McCrossan Over a year ago

@DanMad no problem, glad to help

Duncan Thacker Over a year ago

@Rory I'm agreeing with you and suggesting further steps DanMad might take to help reduce the problem in general. Sorry for the confusion.

Rory McCrossan Over a year ago

Ahhh got you :) I'll delete my comment to avoid confusion for any future visitors

|

Suren Srapyan · Accepted Answer · 2017-08-31 13:05:57Z

2

You can use default parameters starting from ES6/ES2015. The only issue is that you need to rename your input parameters.

var s = 400,
    m = 500,
    l = 700,
    xl = 960;

function breakpoints(_s = s, _m = m, _l = l, _xl = xl) {
  return {
    s: _s,
    m: _m,
    l: _l,
    xl: _xl
  };
};

console.log(breakpoints());

edited Aug 31, 2017 at 13:05

answered Aug 31, 2017 at 13:00

Suren Srapyan

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Comments

kyun · Accepted Answer · 2017-08-31 13:01:09Z

1

var s = 400,
    m = 500,
    l = 700,
    xl = 960;

console.log(breakpoints(s,m,l,xl));

function breakpoints(s, m, l, xl) {
  return {
    s: s,
    m: m,
    l: l,
    xl: xl
  };
};

answered Aug 31, 2017 at 13:01

kyun

10.4k9 gold badges36 silver badges79 bronze badges

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