Tutorial: JavaScript lookup table
November 4, 2023
A lookup table in JavaScript is an object or array used to map keys to values, providing a way to efficiently retrieve data without using conditional statements. This guide outlines methods to create and use lookup tables for various scenarios.
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
const fruitColors = { apple: 'red', banana: 'yellow', cherry: 'red', };
Using Map for diverse key types
const items = new Map([ [1, 'number'], ['one', 'string'], [true, 'boolean'], ]);
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
const errorCodeLookup = { 400: 'Bad Request', 401: 'Unauthorized', 404: 'Not Found', 500: 'Internal Server Error', };
Nested object lookup table
const carModels = { tesla: { modelS: 'electric', model3: 'electric', }, ford: { focus: 'combustion', mustang: 'combustion', }, };
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
let userRoles = {}; users.forEach(user => { userRoles[user.id] = user.role; });
Populating a Map dynamically
let productInventory = new Map(); products.forEach(product => { productInventory.set(product.id, product.quantity); });
You could ship faster.
Imagine the time you'd save if you never had to build another internal tool, write a SQL report, or manage another admin panel again. Basedash is built by internal tool builders, for internal tool builders. Our mission is to change the way developers work, so you can focus on building your product.
Accessing values in a lookup table
Retrieving values is straightforward: for objects, use the dot notation or bracket notation; for Maps, use the get
method.
Accessing values from an object
const color = fruitColors.apple; // 'red' // Or using bracket notation for dynamic keys const key = 'banana'; const color = fruitColors[key]; // 'yellow'
Accessing values from a Map
const itemType = items.get(1); // 'number'
Handling missing keys in a lookup table
When a key is not found, a JavaScript object will return undefined
, while a Map will do the same. You may want to provide a default value.
Providing default values for objects
const getColor = (fruit) => fruitColors[fruit] || 'unknown';
Providing default values for Maps
const getType = (key) => items.get(key) || 'unknown';
Using functions as values
Functions can also be stored in lookup tables, allowing you to associate keys with operations.
const operations = { add: (a, b) => a + b, subtract: (a, b) => a - b, }; const result = operations.add(5, 3); // 8
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.
const sparseArray = []; sparseArray[10] = 'ten'; sparseArray[20] = 'twenty';
Conclusion
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.
TOC
November 4, 2023
A lookup table in JavaScript is an object or array used to map keys to values, providing a way to efficiently retrieve data without using conditional statements. This guide outlines methods to create and use lookup tables for various scenarios.
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
const fruitColors = { apple: 'red', banana: 'yellow', cherry: 'red', };
Using Map for diverse key types
const items = new Map([ [1, 'number'], ['one', 'string'], [true, 'boolean'], ]);
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
const errorCodeLookup = { 400: 'Bad Request', 401: 'Unauthorized', 404: 'Not Found', 500: 'Internal Server Error', };
Nested object lookup table
const carModels = { tesla: { modelS: 'electric', model3: 'electric', }, ford: { focus: 'combustion', mustang: 'combustion', }, };
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
let userRoles = {}; users.forEach(user => { userRoles[user.id] = user.role; });
Populating a Map dynamically
let productInventory = new Map(); products.forEach(product => { productInventory.set(product.id, product.quantity); });
You could ship faster.
Imagine the time you'd save if you never had to build another internal tool, write a SQL report, or manage another admin panel again. Basedash is built by internal tool builders, for internal tool builders. Our mission is to change the way developers work, so you can focus on building your product.
Accessing values in a lookup table
Retrieving values is straightforward: for objects, use the dot notation or bracket notation; for Maps, use the get
method.
Accessing values from an object
const color = fruitColors.apple; // 'red' // Or using bracket notation for dynamic keys const key = 'banana'; const color = fruitColors[key]; // 'yellow'
Accessing values from a Map
const itemType = items.get(1); // 'number'
Handling missing keys in a lookup table
When a key is not found, a JavaScript object will return undefined
, while a Map will do the same. You may want to provide a default value.
Providing default values for objects
const getColor = (fruit) => fruitColors[fruit] || 'unknown';
Providing default values for Maps
const getType = (key) => items.get(key) || 'unknown';
Using functions as values
Functions can also be stored in lookup tables, allowing you to associate keys with operations.
const operations = { add: (a, b) => a + b, subtract: (a, b) => a - b, }; const result = operations.add(5, 3); // 8
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.
const sparseArray = []; sparseArray[10] = 'ten'; sparseArray[20] = 'twenty';
Conclusion
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.
November 4, 2023
A lookup table in JavaScript is an object or array used to map keys to values, providing a way to efficiently retrieve data without using conditional statements. This guide outlines methods to create and use lookup tables for various scenarios.
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
const fruitColors = { apple: 'red', banana: 'yellow', cherry: 'red', };
Using Map for diverse key types
const items = new Map([ [1, 'number'], ['one', 'string'], [true, 'boolean'], ]);
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
const errorCodeLookup = { 400: 'Bad Request', 401: 'Unauthorized', 404: 'Not Found', 500: 'Internal Server Error', };
Nested object lookup table
const carModels = { tesla: { modelS: 'electric', model3: 'electric', }, ford: { focus: 'combustion', mustang: 'combustion', }, };
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
let userRoles = {}; users.forEach(user => { userRoles[user.id] = user.role; });
Populating a Map dynamically
let productInventory = new Map(); products.forEach(product => { productInventory.set(product.id, product.quantity); });
You could ship faster.
Imagine the time you'd save if you never had to build another internal tool, write a SQL report, or manage another admin panel again. Basedash is built by internal tool builders, for internal tool builders. Our mission is to change the way developers work, so you can focus on building your product.
Accessing values in a lookup table
Retrieving values is straightforward: for objects, use the dot notation or bracket notation; for Maps, use the get
method.
Accessing values from an object
const color = fruitColors.apple; // 'red' // Or using bracket notation for dynamic keys const key = 'banana'; const color = fruitColors[key]; // 'yellow'
Accessing values from a Map
const itemType = items.get(1); // 'number'
Handling missing keys in a lookup table
When a key is not found, a JavaScript object will return undefined
, while a Map will do the same. You may want to provide a default value.
Providing default values for objects
const getColor = (fruit) => fruitColors[fruit] || 'unknown';
Providing default values for Maps
const getType = (key) => items.get(key) || 'unknown';
Using functions as values
Functions can also be stored in lookup tables, allowing you to associate keys with operations.
const operations = { add: (a, b) => a + b, subtract: (a, b) => a - b, }; const result = operations.add(5, 3); // 8
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.
const sparseArray = []; sparseArray[10] = 'ten'; sparseArray[20] = 'twenty';
Conclusion
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.
What is Basedash?
What is Basedash?
What is Basedash?
Ship faster, worry less with Basedash
Ship faster, worry less with Basedash
Ship faster, worry less with Basedash
You're busy enough with product work to be weighed down building, maintaining, scoping and developing internal apps and admin panels. Forget all of that, and give your team the admin panel that you don't have to build. Launch in less time than it takes to run a standup.
You're busy enough with product work to be weighed down building, maintaining, scoping and developing internal apps and admin panels. Forget all of that, and give your team the admin panel that you don't have to build. Launch in less time than it takes to run a standup.
You're busy enough with product work to be weighed down building, maintaining, scoping and developing internal apps and admin panels. Forget all of that, and give your team the admin panel that you don't have to build. Launch in less time than it takes to run a standup.
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