November 4, 2023
Understanding the concept of a lookup table
Before diving into creating a lookup table, it's essential to understand its purpose. A lookup table serves as a data structure that replaces runtime computations with a simpler array or object lookup, often resulting in more efficient code.
Choosing the right data structure for your lookup table
Depending on the nature of the keys and values you are working with, you can choose between an object or a Map. Objects are suitable for string or symbol keys, while Maps can handle a broader range of key types, including objects and functions.
Using objects for string-based keys
Using Map for diverse key types
Creating a static lookup table
Static lookup tables are predefined and do not change at runtime. You define all the keys and values upfront.
Simple object-based lookup table
Nested object lookup table
Creating a dynamic lookup table
Dynamic lookup tables are built at runtime, often from data fetched from an API or user input.
Populating an object dynamically
Populating a Map dynamically
Accessing values in a lookup table
Retrieving values is straightforward: for objects, use the dot notation or bracket notation; for Maps, use the
Accessing values from an object
Accessing values from a Map
Handling missing keys in a lookup table
undefined, while a Map will do the same. You may want to provide a default value.
Providing default values for objects
Providing default values for Maps
Using functions as values
Functions can also be stored in lookup tables, allowing you to associate keys with operations.
Optimizing lookup tables for performance
To optimize a lookup table, ensure the keys are easily hashable and the table is not overly large, which can slow down key lookup times.
Using sparse arrays wisely
Sparse arrays can serve as lookup tables with integer keys, but they should be used judiciously as they can lead to performance issues.
Lookup tables in JS offer a powerful way to streamline data retrieval by mapping keys to values. By choosing the right structure and populating it thoughtfully, you can enhance both the performance and readability of your code.
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