object properties as key value pairs in hash function

Question

I have a basic question regard to Javascript.

as Javascript do not have hash table objects, but I realize that I can just build a object to use it as a hash table like the following:

var hashtable = {
    Today : {"I", "feel", "good"},
    Tomorrow : {'is', 'another', 'day'},
    Yesterday : 'alwaysGood'
}

I have search a lot on the Internet, there are some means which using associativeArray or which build its own object as a hash table, is the above native object building method not good？

Well you cannot do exactly what you've posted, as it's syntactically incorrect. However the basic idea of using an object like a hash table is fine. — Pointy, May 13 '14 at 15:11
^^ What he said, the idea is fine, but your code is invalid, and there are no associative arrays in javascript. — adeneo, May 13 '14 at 15:14
@adeneo Objects *are* [associative arrays](http://en.wikipedia.org/wiki/Associative_array) — Andrew Vermie, May 13 '14 at 15:21
@AndrewVermie Technically, no, they're not -- but they can be used like associative arrays in other languages are used. — Blazemonger, May 13 '14 at 15:41
possible duplicate of [What's the difference between objects and associated array in javascript?](http://stackoverflow.com/questions/8146104/whats-the-difference-between-objects-and-associated-array-in-javascript) — zmo, May 13 '14 at 15:48

score 2 · Accepted Answer · answered May 13 '14 at 15:20

Your code sample is not valid JavaScript because of this {"I", "feel", "good"}. In this context, the curly braces represent an object literal, and each of the object's properties must be assigned a value.

A valid version would look like:

var hashtable = {
    Today : ["I", "feel", "good"],
    Tomorrow : ['is', 'another', 'day'],
    Yesterday : 'alwaysGood'
}

Note the use of [] which creates an array. Arrays in JavaScript are numerically keyed, there is no concept of an associative array like there is in other languages. However, a JavaScript array itself, is also an object, so you can freely add properties:

var arr = [];
arr.Today = 'some value';

To avoid the use of an array in your example, you would need to set values for all properties:

var hashtable = {
    Today : {"I" : "i val", "feel" : "feel val", "good" : "good val"},
    Tomorrow : {'is' : 'is val', 'another' : 'another val', 'day' : 'day val'},
    Yesterday : 'alwaysGood'
}

Using objects in this way is valid and acceptable. For more information refer to Working With Objects (MDN).

object properties as key value pairs in hash function

1 Answers1