How to Dynamically Create Keys in JavaScript Objects?

Creating Dynamic Keys in JavaScript Objects

When attempting to create a dynamic key for a JavaScript object, users may encounter issues when using dot notation. This article addresses this challenge and explores the alternative method of using square brackets.

Square Brackets Approach

To create a dynamic key using square brackets, follow this syntax:

jsObj['key' + i] = 'example' + 1;

This method operates by treating the property name as a computed string, allowing for the assignment of dynamic keys.

Understanding Array and Object Properties

Arrays in JavaScript exhibit special behavior regarding numeric property names. The length property of an array reflects the maximum numeric property value. When setting a numeric property on an array, the length property is updated accordingly.

In contrast, plain objects do not exhibit this behavior. Setting a numeric property on an object does not affect its length property.

Advantages and Considerations

Using square brackets offers the following advantages:

• Enables the creation of dynamic keys in objects.
• Maintains the integrity of the length property in arrays.

However, consider the potential implications of array serialization. Array instances serialized to JSON only include numerically-named properties. If additional properties are added, they may be lost upon serialization.

ES2015 Computed Property Names

ES2015 introduces Computed Property Names, providing an elegant solution for creating dynamic keys:

var key = 'DYNAMIC_KEY',
    obj = {
        [key]: 'ES6!'
    };

This approach allows for the assignment of dynamic keys without explicitly constructing string concatenations.

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