Javascript hash object as key
Here is a proposal: Show
The API is exactly as shown in your question. You can't play with the reference in js however (so two empty objects will look like the same to the hashtable), because you have no way to get it. See this answer for more details: How to get javascript object references or reference count? Jsfiddle demo: http://jsfiddle.net/HKz3e/ However, for the unique side of things, you could play with the original objects, like in this way:
Jsfiddle demo: http://jsfiddle.net/HKz3e/2/ This means that your objects need to have a property named It also means you are limited on the number of items you can store in this hashtable. Limited to 253, that is. And now, the "it's not going to work anywhere" solution: use ES6 WeakMaps. They are done exactly for this purpose: having objects as keys. I suggest you read MDN for more information: https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/WeakMap It slightly differs from your API though (it's
Jsfiddle demo with a weakmap shim: http://jsfiddle.net/Ralt/HKz3e/9/ However, weakmaps are implemented in FF and Chrome (only if you enable the "Experimental javascript features" flag in chrome however). There are shims available, like this one: https://gist.github.com/1269991. Use at your own risk. You can also use Hash Tables are a data structure that allow you to create a list of paired values. You can then retrieve a certain value by using the key for that value, which you put into the table beforehand. A Hash Table transforms a key into an integer index using a hash function, and the index will decide where to store the key/value pair in memory: Hash table for storing phone books (from Wikipedia)You'll commonly use a Hash Table because of its fast search, insertion, and delete operations:
Source from Wikipedia This tutorial will help you understand Hash Table implementation in JavaScript as well as how you can build your own Hash Table class. First, let's look at JavaScript's How to Use Hash Tables with Object and Map Classes in JavaScriptThe
most common example of a Hash Table in JavaScript is the In the following example, the key JavaScript object is an example of Hash Table implementationBut JavaScript's
For example, the JavaScript object
inherited method call exampleJavaScript doesn't block an attempt to overwrite the JavaScript object inherited property gets overwrittenTo handle these shortcomings, JavaScript created another implementation of the Hash Table data structure which is called Just like JavaScript Map class is another implementation of Hash TableUnlike the You also can't overwrite Map type property can't be overwrittenAs you can see from the code above, you can't add a new entry to the The Iterating through a Map objectNow that you've learned how JavaScript implements Hash Tables in the form of How to Implement a Hash Table Data Structure in JavaScriptAlthough JavaScript already has two Hash Table implementations, writing your own Hash Table implementation is one of the most common JavaScript interview questions. You can implement a Hash Table in JavaScript in three steps:
Alright, let's start with creating the HashTable class initial propertiesAll your key/value pairs will be stored inside the
How to write the hash() methodNext, you need to create the A simple way to create the hash would be to sum the ASCII code of the characters in the key using the
But since the To ensure that the hash value doesn't exceed the bucket size, you need to use the modulo operator as shown below:
Now that you have the How to write the set() methodTo set the key/value pair in your Hash Table, you need to write a
Now that the How to write the get() methodTo get a certain value from the Hash Table, you
need to write a
This way, the So far so good. Let's add another method to delete key/value pair from the Hash Table next. How to write the remove() methodTo delete a key/value pair from the Hash Table, you need to write a
With that, you now have a working How to Test the Hash Table ImplementationIt's time to test the Hash Table implementation. Here's the full code for the Hash Table implementation again: The HashTable implementation in JavaScriptTo test the Testing HashTable set() methodThen, let's try to retrieve them using the Testing HashTable get() methodFinally, let's try to delete one of these values with the
Testing HashTable remove() methodAlright, all the methods are working as expected. Let's try another insertion with a new Hash Table index collision Oops! Looks like we got into some trouble here. 😨 How to Handle Index CollisionSometimes, the hash function in a Hash Table may return the same The same Right now, the data stored in our Hash Table implementation looks as follows:
To handle the
To create the second array, you need to update the
The complete
Next, update the
Finally, you need to update the
With that, your As a bonus, let's add a
Here's the complete Complete HashTable class implementationYou can test the implementation by creating a new Another HashTable testNow there's no collision inside the ConclusionIn this tutorial, you've learned what a
Hash Table is and how JavaScript uses it to create the You've also learned how to implement your own By using a Hash Table data structure, you will be able to create an associative array with fast search, insertion, and delete operations. 😉 Thanks for reading this tutorialIf you want to learn more about JavaScript, you may want to check out my site at sebhastian.com, where I have published over 100 tutorials about programming with JavaScript, all using easy-to-understand explanations and code examples. The tutorials include String manipulation, Date manipulation, Array and Object methods, JavaScript algorithm solutions, and many more. Learn to code for free. freeCodeCamp's open source curriculum has helped more than 40,000 people get jobs as developers. Get started Can you use an object as a key JavaScript?Can you use objects as Object keys in JavaScript? # The short answer is "no". All JavaScript object keys are strings.
Can we use object as key in hashmap JavaScript?JavaScript Objects: Similar but Different
The key in a hashmap can be any datatype, this includes arrays and objects. Meanwhile, objects can only use integers, strings, and symbols as their keys. Hashmaps are organized as linked lists, so the order of its elements is maintained, which allows the hashmap to be iterable.
Is object in JavaScript hash?A JavaScript Object is an example of a Hash Table because data is represented a key/value pairs. A hashing function can be used to map the key to an index by taking an input of any size and returning a hash code identifier of a fixed size.
What is hash key in JavaScript?A hash function is a method or function that takes an item's key as an input, assigns a specific index to that key and returns the index whenever the key is looked up. This operation usually returns the same hash for a given key. A good hash function should be efficient to compute and uniformly distribute keys.
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