In programming, lookup tables are used to map inputs to outputs. If you’ve ever used a dictionary to look up a word or searched for an item in an index, then you’ve used a lookup table.
In this article, we’ll explore what a lookup table is and how it can be used in JavaScript to make programming easier and more efficient. What is a Lookup Table?
A lookup table is a data structure that maps inputs to outputs. It is commonly used when there is a known set of inputs and outputs, and the output can be determined without computation.
Look up tables are used widely in programming because they offer an efficient way to retrieve information.
Using Objects for Lookup Tables in JavaScript
In JavaScript, a lookup table can be implemented using an object. An object is a collection of key-value pairs.
When an object is used for lookup tables, the keys represent the input values, and the values represent the output values. Using objects for lookup functions allows for direct addressing, which offers quick and efficient retrieval of information.
Example of Using a Lookup Table
Let’s say you are designing an e-commerce website that displays prices based on user-selected filters. A user can filter products based on different criteria, such as size, brand, and color.
The website has a database of products, and each product has a name, price, size, brand, and color. When a user selects a filter, the website needs to display only the products that match the filter.
The prices of the products also need to be displayed on the page. To make this process more efficient, we can use a lookup table to index products based on commonly used filters.
Let’s say we have a JavaScript object called DBProductArray, which contains all the products in the database. We can create a lookup table to index products based on their size, brand, and color.
Here is an example of how we can use the lookup table for products based on size:
“`
let sizeLookup = {};
DBProductArray.forEach((product) => {
if (!sizeLookup[product.size]) {
sizeLookup[product.size] = [];
}
sizeLookup[product.size].push(product);
});
“`
In the first line, we create an empty object called sizeLookup. We then loop through each product in the database, and for each product, we check if the product’s size already exists in the sizeLookup object.
If it doesn’t, we create a new array for that size. We then push the product into the array that matches its size.
Now that we have a lookup table for products based on size, we can use it to display prices of products that match a particular size. Here is an example of how we can do this:
“`
let selectedSize = ‘Large’;
let products = sizeLookup[selectedSize];
products.forEach((product) => {
console.log(product.price);
});
“`
In the first line, we set the selectedSize variable to “Large”.
We then retrieve the array of products that match the selected size from the sizeLookup object. Finally, we loop through each product in the array and display its price.
We can create similar lookup tables for filtering products based on brand and color. Using lookup tables to index products based on commonly used filters improves the website’s performance by reducing the need to iterate through the entire database every time a new filter is selected.
Conclusion
Lookup tables are a powerful tool in programming, as they offer an efficient way to retrieve information. In JavaScript, objects can be used as lookup tables to provide direct addressing, which allows for quick and efficient retrieval of information.
By using lookup tables, we can improve the performance of our programs and make them more efficient.
3) Implementation of a Lookup Table in JavaScript
In the previous section, we saw how lookup tables can be implemented using objects in JavaScript. In this section, we’ll explore how to create a lookup table for an e-commerce website using JavaScript.
We’ll start by assuming that we have a database of products called DBProductArray. Each product in the database has a name, price, size, brand, and color.
We want to create a lookup table for our website that allows users to filter products based on color and size.
Looping through the DBProductArray to Create the Lookup Table
To create a lookup table, we need to loop through the DBProductArray and add keys and nested objects to the lookup table based on color and size information. Here’s an example of how we can create the lookup table based on size information:
“`
let sizeLookup = {};
DBProductArray.forEach((product) => {
if (!sizeLookup[product.size]) {
sizeLookup[product.size] = {};
}
sizeLookup[product.size][product.name] = product.price;
});
“`
In the first line, we create an empty object called sizeLookup to store the lookup table.
We then loop through each product in the DBProductArray and check if the product’s size is already a key in the sizeLookup object. If it isn’t, we create a new nested object for that size.
We then add a key-value pair to the nested object, where the key is the product name and the value is the product price. With the above code, we have created a lookup table for products based on their size.
We can also create a lookup table for products based on their color. Here’s an example of how we can create the lookup table based on color information:
“`
let colorLookup = {};
DBProductArray.forEach((product) => {
if (!colorLookup[product.color]) {
colorLookup[product.color] = {};
}
colorLookup[product.color][product.name] = product.price;
});
“`
This code is similar to the previous one, except that we’re now using the product’s color to create keys in the lookup table.
Adding Keys and Nested Objects to the Lookup Table Based on Color and Size Information
In the above examples, we created lookup tables based on size and color information. While these lookup tables will be useful for filtering products based on size and color, they don’t allow us to filter products based on both size and color.
To filter products based on both size and color, we need to create a nested lookup table that uses both size and color information. Here’s an example of how we can create a nested lookup table based on size and color information:
“`
let sizeAndColorLookup = {};
DBProductArray.forEach((product) => {
if (!sizeAndColorLookup[product.size]) {
sizeAndColorLookup[product.size] = {};
}
if (!sizeAndColorLookup[product.size][product.color]) {
sizeAndColorLookup[product.size][product.color] = {};
}
sizeAndColorLookup[product.size][product.color][product.name] = product.price;
});
“`
In the first two lines, we create empty objects for the size and color keys in the lookup table.
We then add an extra nested object that groups products by both size and color. Finally, we add the product name and price to the nested object.
By creating nested lookup tables based on color and size information, we can filter products based on a combination of both size and color.
4) Benefits of Using a Lookup Table
Using a lookup table offers many benefits, especially in applications where we need to search for information quickly. Here are two main benefits of using lookup tables:
Speeding Up Search Result Queries and Improving Performance
In an e-commerce website, we can use a lookup table to create search results based on the user’s filter criteria, such as size and color. Having a lookup table allows us to retrieve matching products quickly, without having to iterate through the entire database.
This improves the website’s performance and the user experience.
Viewing Product Pricing Information Without Querying the Database
When a user selects a filter on an e-commerce website, the website needs to show products that match those filters. With a lookup table, we can display pricing information without having to query the database.
This is because the lookup table already contains the pricing information, and we can therefore display the product and price information faster. Another benefit of using lookup tables is that it allows us to store repetitive data in a more efficient way.
For example, instead of having to store the price of each product multiple times in the database, we can store it once in the lookup table and reference it whenever it’s needed. This way, we can reduce the size of the database and improve the overall performance of the application.
Conclusion
Lookup tables are powerful tools that can be used to create efficient and fast applications. In this article, we explored how to create lookup tables using JavaScript objects and demonstrated the benefits of using lookup tables in an e-commerce website.
By using lookup tables, we can improve the performance of our applications, reduce the size of our database and provide our users with a better user experience. In conclusion, a lookup table is a data structure that maps inputs to outputs, and it offers an efficient way to retrieve information in programming.
In JavaScript, lookup tables can be implemented using objects that provide direct addressing and enable quick retrieval of data. An example of using a lookup table is an e-commerce website that displays product prices based on user-selected filters.
Using lookup tables can increase the performance of the application, improve user experience, and efficiently store repetitive data. By utilizing lookup tables, programmers can create efficient and fast applications that enhance the user experience.