How to Access JavaScript Object Properties Using a String for the Property Name?

Accessing JavaScript Object Property by Name as String

When working with JavaScript objects, it's often necessary to access properties by their names, which can be obtained dynamically or from user input. This question addresses how to write a function to retrieve a property value based on its name represented as a string.

Solution

The provided solution offers two approaches:

Bracket Notation:

This is the preferred method for accessing properties by name dynamically. It involves using brackets ([]), like:

var side = columns['right'];

Function (using bracket notation):

If you specifically require a function, you can use:

function read_prop(obj, prop) {
    return obj[prop];
}

Nested Objects

If your object is nested, you can access property values using multiple brackets. For example, with the object:

var foo = { a: 1, b: 2, c: { x: 999, y: 998, z: 997 } };

you can access the property x like this:

var cx = foo['c']['x'];

Undefined Properties

If an attempted property reference results in an undefined property, it will return undefined (not null or false). For instance:

foo['c']['q'] === null // returns false
foo['c']['q'] === false // returns false
foo['c']['q'] === undefined // returns true

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