Implementing vectors in JavaScript

Tuesday, Jan 14, 2020
JavaScript DataStructures

Vector is one of the simplest data structures with the following properties:

fixed size
ordered: elements are arranged sequentially, one after the other
finite size: zero or finite integer number of elements

This is similar to what arrays in C are and is easy to visualize how they relate to computer memory (sequentially arranged blocks to store data).

Vector Operations

new Vector(n) // create a vector n elements
LENGTH(v)     // get the length of the vector, i.e. the number of elements
v[i]          // read the value at index i
v[i] = o      // store o at index i

I used arrays and objects in JavaScript to implement the above functionality.

JavaScript Implementation

// vector.js -- constructing vectors in JavaScript
function Vector(length)
{
    this.length = length;
    this.data = new Array(length);
}

v1 = new Vector(3); // create a new instance of Vector
console.log(v1);

// method to set the value of index i to x
Vector.prototype.set = function(x, i)
{
    if (i < this.length)
        this.data[i] = x;
    else
        console.log("Error! Index out of bounds: " , 
            i , "> " , this.length - 1);
}

// testing the set method
for (var i = 0; i < v1.length; i++)
    v1.set(i*i - i, i);
console.log(v1);
v1.set(15, 13); // cannot assign 15 since index(13) is out of bounds

// method to get the value of index i
Vector.prototype.get = function(i)
{
    if (i < this.length)
        console.log(this.data[i]);
    else
        console.log("Error! Index out of bounds: " , 
            i , "> " , this.length - 1);
}

// testing the get method
v1.get(2);
v1.get(5);

Output

Vector { length: 3, data: [ <3 empty items> ] }
Vector { length: 3, data: [ 0, 0, 2 ] }
Error! Index out of bounds:  13 >  2
2
Error! Index out of bounds:  5 >  2