Building Web-Based Games and Utility Projects Using JavaScript/

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Graph Data Creation and Rendering

Graph Data Creation and Rendering

Implement the functionality to create the graph data for the problem statement and render it on the HTML web page.

We'll cover the following...

Introduction

Now let's start implementing our travel planner project. We'll follow the steps mentioned below to build the project:

  1. Create the data for the project. This data is just the graph with cities as nodes, the route to travel from one city to another as edges, and the time taken to travel from one city to another as weights. There will be two types of routes from one city to another, namely the route taken when going by bus and the route taken when flying. We will add some randomness to our graphs so that the structure of the graphs differs for each run.

  2. We will create the UI and partition it into two vertical sections. On the left side, we will display the graph generated using the logic written in the previous step. We will complete the logic for the right side in the later part of the chapter.

Now let's start implementing the functionalities.

Create the graph data for the project

Let's create a function to generate the graph data. The function is going to be almost the same as discussed in the Visualize Graphs Using Vis.js lesson, with some minor differences. Here's the code:

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// List of cities
const cities = ["New York", "Denver", "California", "San Fransisco", "Las Vegas", 
                "Seattle", "Chicago", "Los Angeles", "Dallas", "Columbus"];
// Function to create data for our travel planner project
function createDataForTravelPlanner(){
    // Initialising number of nodes in the graph dynamically
    numVertices = Math.floor(Math.random() * cities.length) + 1;
    // Create data for vertices
    let vertices = [];
    for(let i = 1; i <= numVertices; i++){
        // Storing the id and the name of the city
        vertices.push({ id: i, label: cities[i - 1] })
    }
    // Creating data for edges
    let edges = [];
    for(let i = 2; i <= numVertices; i++) {
    
        // Randomly picking a neighbour node from 0 to i - 1 to create an edge
        let neighbour = i - Math.floor(Math.random() * Math.min(i - 1, 3) + 1);
        // Adding the edge between the node and the  neighbour
        edges.push({ type: 0, // 0 denotes bus route and 1 denotes air route
                     from: i, // the node 
                     to: neighbour, // the neighbour
                     color: 'orange',  // color of the edge
                     label: String(Math.floor(Math.random() * 70) + 30)  //random distance 
                    });
    }
    // We will use these variables in later part of the chapter
    src = 1;
    dst = numVertices;
    // Add randomness to the edges in the graph
    for(let i = 1; i <= numVertices/2; ){
        // Generate two random integers in the range of 1 to numVertices
        let n1 = Math.floor(Math.random() * numVertices) + 1;
        let n2 = Math.floor(Math.random() * numVertices) + 1;
        if(n1 != n2) {
            if(n1 < n2) {
                // swap n1 and n2 to make n1 larger than n2
                let tmp = n1;
                n1 = n2;
                n2 = tmp;
            }
            // Create a flag to store three states:
            // 1. Assign value of 0 if there is no edge between n1 and n2
            // 2. Assign value of 1 if there is an edge denoting the bus route
            // 3. Assign value of 2 if there is an edge denoting the aeroplane route
            let typeOfEdge = 0;
            // Iterate for all the edges
            for(let j = 0; j < edges.length; j++) {
                // Check if edge between n1 and n2 already exists
                if(edges[j]['from'] === n1 && edges[j]['to'] === n2) {
                    
                    // Check for the bus route
                    if(edges[j]['type'] === 0)
                        typeOfEdge = 1; // flag to denote bus route exist
                    else
                        typeOfEdge = 2; // flag to denote air route exist
                }
            }
            // Check if a bus or no route exists between n1 and n2
            if(typeOfEdge <= 1) {
                
                // If no route exists
                if (typeOfEdge === 0 && i < numVertices / 4) {
                    // Create an edge between n1 and n2
                    edges.push({
                            type: 0,
                            from: n1,
                            to: n2,
                            color: 'orange',
                            label: String(Math.floor(Math.random() * 70) + 30)
                    });
                } else {
                    // Create an edge for air route between n1 and n2
                    edges.push({
                            type: 1,
                            from: n1,
                            to: n2,
                            color: 'green',
                            label: String(Math.floor(Math.random() * 50) + 1)
                    });
                }
                i++;
            }
        }
    }
    // Creating the data object for vis
    let data = {
        nodes: vertices,
        edges: edges
    };
    // Return the final object containing the information for the graph
    return data;
}
const graphData = createDataForTravelPlanner();
console.log(graphData);

Explanation

We'll only explain the highlighted code in the above code snippet, because the rest of the code is ...