JavaScript: Dynamically generate tables and calculate column sums
This document is intended to guide beginners to dynamically generate HTML tables using JavaScript, calculate the sum of each column, and finally add the sum to the bottom of the table as a new row. Through this article, you will learn how to manipulate DOM elements with JavaScript, create tables, and perform simple numerical calculations.
Dynamically generate tables and calculate column sums
In web development, it is often necessary to dynamically generate tables and perform some calculations. This tutorial demonstrates how to create a table using JavaScript that calculates the sum of squares of the number entered by the user, and displays the results in the table. Finally, we will also calculate the sum of each column and add it to the bottom of the table.
1. HTML structure
First, we need to create an input box, a button, and a div element in HTML that displays the results:
<input id="broj" type="text"> <button onclick="tablica()">Generate table</button> <div id="rezultat"></div>
2. JavaScript code
Next, we will write JavaScript code to implement table generation and calculation.
function tablica() {
var sum1 = 0, sum2 = 0, sum3 = 0; // Initialize the sum of columns var nr = document.getElementById("broj").value; // Get the number entered by the user// Input verification if (nr <tr>
<th>N</th>
<th>N²</th>
<th>N!</th>
</tr>";
var faktorijela = 1; // Initialize factorials// Loop to generate table rows for (var i = 1; i <td>" val1 "</td><td>" val2 "</td><td>" val3 "</td>";
// Accumulated column sum1 = sum1 val1;
sum2 = sum2 val2;
sum3 = sum3 val3;
}
// Add sum line rez = rez "<tr>
<td>" sum1 "</td>
<td>" sum2 "</td>
<td>" sum3 "</td>
</tr>";
rez = rez "";
// Show the table on the page var rezTablica = document.getElementById("rezultat");
rezTablica.innerHTML = rez;
}
Code explanation:
- Initialize variables:
- sum1, sum2, sum3: is used to store the sum of each column, with an initial value of 0.
- nr: Gets the number entered by the user in the input box.
- rez: Used to build HTML table strings.
- faktorijela: is used to calculate factorial, with an initial value of 1.
- Input Verification: Check whether the user input is less than 2. If it is less than 2, an error message is displayed and the function execution ends.
- Create table header: Use HTML string to create the header of the table, including three columns "N", "N²", "N!".
- Loop to generate table rows:
- Use the for loop to iterate from 1 to the number nr entered by the user.
- In each iteration, the square (i * i) and factorial (faktorijela = faktorijela * i) of the current number are calculated.
- Use HTML string to create a row of the table, containing the current number, squares, and factorials.
- Add this line to the rez string.
- Accumulate the three values of the current row into sum1, sum2, and sum3 respectively.
- Add sum row: After the loop is finished, create the last row of the table using an HTML string, containing the sum of each column.
- Show table: Assign the complete HTML table string to the innerHTML property of the rezultat div to display the table on the page.
3. Operation results
When the user enters a number (for example, 5) in the input box and clicks the "Generate Table" button, the page will display a table with 5 rows of data, and a row will display the sum of each column at the bottom of the table.
4. Things to note
- Data type: Make sure that the user is entering a number. You can use the parseInt() or parseFloat() functions to convert the value in the input box into a number.
- Error handling: More error handling mechanisms can be added, such as checking whether the user has entered non-numeric characters.
- Style beautification: You can use CSS to beautify the style of a table.
- Code reuse: The logic that generates the table can be encapsulated into an independent function, which is convenient for calling in other places.
5. Summary
With this tutorial, you learned how to dynamically generate HTML tables using JavaScript and calculate the sum of each column. This is just a simple example that you can expand and modify according to actual needs. Hope this tutorial is helpful to you!
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