JavaScript Object vs. Map
Map was introduced in ES6, while Object was traditionally used as a Map before ES6. The newly introduced Map has several key differences compared to the original Object:
Map Advantages
Map has no prototype, making it safer and preventing accidental key naming conflicts
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Map is more secure: When setting user-provided key-value pairs with an Object, attackers could potentially overwrite the Object’s prototype, leading to object injection attacks.
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Map prevents accidental key naming conflicts: With Objects, you need to be cautious about default keys that might conflict with your custom keys.
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Note: While these issues can be resolved using
Object.create(null), this approach is rarely used in practice.
Map keys can be any value, while Object keys are limited to String or Symbol
Map prevents accidental naming conflicts caused by automatic key conversion to String: When working with key-value pairs, developers often use various data types as keys. However, in JavaScript, when using Objects, any key is automatically converted to a string, which can lead to errors. For example, two originally different keys might become identical strings after conversion, resulting in key collision issues. Map objects solve this problem by allowing developers to use any value as a key.
Map supports iteration
We can directly iterate over a Map using for...of or forEach, while iterating over an Object requires additional methods like Object.entries or Object.keys.
Map keys maintain insertion order
As mentioned above, Map is iterable and maintains the order of elements during iteration. When using Objects, even with helper methods like Object.entries or Object.keys, the iteration results might not follow the original insertion order. This ordered behavior makes Map objects particularly useful in algorithms where maintaining order is crucial.
Map provides convenient methods for key-value pair operations
For example, Map has a simple size method to determine the number of key-value pairs, while with Objects, we need to use Object.keys().length. Additionally, Map provides a clear method to remove all key-value pairs at once, whereas with Objects, you would need to delete them individually.
Map performs better for frequent key-value pair modifications
Map is optimized for scenarios requiring efficient lookup, insertion, and deletion operations.
Map Disadvantages
Map lacks native support for serialization and parsing
Objects can be serialized and parsed using JSON.stringify() and JSON.parse() respectively, but Map requires custom implementation for these operations.