Javascript error with setting a default value for function

Question

I have a function:

function modifySpinner(currentIcon, selector, spinType = remove)
{
    if (spinType === 'add') {
        // something
    }
}

But I am receiving this error in my console:

Uncaught SyntaxError: Unexpected token =

This wasn't causing issues in firefox? But in chrome its not working.

kemiller2002 · Accepted Answer · 2015-08-25 15:14:12Z

1

Try this instead:

function modifySpinner(currentIcon, selector, spinType)
{
    var spinType = spinType || "remove" 

    if (spinType === 'add') {
        // something
    }
}

So why this works: if the spinType doesn't have a value it equates to undefined. With var spinType = spinType || "remove" you are saying "hey evaulate spinType and if it's false, then use remove." undefined and null both evaluate to false in this conditional statement so, it's shorthand for saying if this value is undefined, use this other value instead.

Truthy and Falsy in Javascript

answered Aug 25, 2015 at 15:14

kemiller2002

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Comments

Pierre-Alexandre Moller · Accepted Answer · 2015-08-25 15:14:59Z

1

You can't use this syntax for a default value.

function modifySpinner(currentIcon, selector, spinType )
{
  spinType = spinType || "remove";
  if (spinType === 'add') {
      // something
  }
}

Like this, if it's undefined, null, ... The value will be remove

answered Aug 25, 2015 at 15:14

Pierre-Alexandre Moller

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Comments

aghidini · Accepted Answer · 2015-08-25 15:15:17Z

0

Javascript doesn't have default parameters (it's been introduced in Ecmascript 6), you have to do the check yourself:

function modifySpinner(currentIcon, selector, spinType)
{
    spinType = typeof spinType  !== 'undefined' ? spinType : 'remove';
    if (spinType === 'add') {
        // something
    }
}

answered Aug 25, 2015 at 15:15

aghidini

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