CODEWITHSUNDEEP
javascriptnode.jscoffeescript
Joshua Michael Calafell
Joshua Michael Calafell

Reputation: 3117

Can additional object properties in coffeescript/javascript be added dynamically to an existing object?

Can additional object properties in coffeescript/javascript be added dynamically to an existing object?

For example:

var fred = { name: "Fred", species: "Sub-Human" };

Now later, for example, I want to add college major to get this:

{ name: "Fred", species: "Sub-Human", major: "Computer Science" }

And... how does this affect, or does it affect performance?

Upvotes: 1

Views: 596

Answers (2)

T.J. Crowder
T.J. Crowder

Reputation: 1075925

Sure, JavaScript objects are completely dynamic.

You can use dot notation with a property name literal:

fred.major = "Computer Science";

or brackets notation with a property name string:

fred["major"] = "Computer Science";

Literals can be optimized more by the JavaScript engine, strings can be the result of any expression (so, fred["m" + "ajo" + "r"] = ... would work) and can include characters (like spaces — yes, really —) that you can't use in a property name literal.

I suggest working through some basic JavaScript tutorials (if you want to learn JavaScript) or CoffeeScript tutorials (if you want to learn CoffeeScript).

Upvotes: 4

Mouser
Mouser

Reputation: 13304

Yes;

fred["major"] = "Computer Science";

All properties on an object can be accessed by using square brackets and the property name. This method also allows you to set new properties.

fred.major = "Computer Science";

This will also work fine.

Upvotes: 2

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