How to inspect an object's property if the property name is an empty string?

Question

Javascript objects' properties can be named with the empty string, for example:

foo = { 
    "" : "bar"
}

Dot notation does not seem to be able to call this property. Console output:

foo.
>> "missing name after . operator"

How would you call the "" property?

Same way you'd access a property that contains anything else that wouldn't be legal JavaScript syntax. — Dave Newton
– Dave Newton, Commented Jun 1, 2015 at 20:40
"An object property name can be any valid JavaScript string, or anything that can be converted to a string, including the empty string." developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/… — Choylton B. Higginbottom
– Choylton B. Higginbottom, Commented Jun 1, 2015 at 20:42
I'm not sure if that comment is directed at me; a valid JavaScript string isn't necessarily valid JavaScript code, which is what the dot notation is. — Dave Newton
– Dave Newton, Commented Jun 1, 2015 at 20:43

Nicholas Thomson · Accepted Answer · 2015-06-01 20:37:27Z

5

Use an empty string as a key with the bracket syntax:

foo[""]

answered Jun 1, 2015 at 20:37

Nicholas Thomson

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Choylton B. Higginbottom · Accepted Answer · 2015-06-01 20:41:13Z

0

This can be accomplished with square bracket notation. Console output:

foo[""]
>> "bar"

Documentation

edited Jun 1, 2015 at 20:41

answered Jun 1, 2015 at 20:38

Choylton B. Higginbottom

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4 Comments

Choylton B. Higginbottom Over a year ago

Anyone know if it's possible with dot notation?

RobG Over a year ago

@meetalexjohnson—no. Dot notation can only be used with property names that are valid identifiers (e.g. something that could be used as a variable name), and "" doesn't fit the criteria.

Dave Newton Over a year ago

@meetalexjohnson Wait, why did you comment on your own answer?

Katana314 Over a year ago

This actually isn't the only type of object key that can't be expressed with dot notation. foo["Now this is a story all about how my life got flipped turned upside down"] = bar; is valid, and you can similarly only access it through square bracket notation.

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