If you have seen some websites, especially some Indian government portals, you would have noticed three small buttons at the top rightmost corner of the page looking something like this: -A A A+. These buttons generally allow website users to change the font size of the entire page or a certain portion of the page to a specific size to improve the readability of the page. In this post, we are going to learn how to achieve this feature for a specific div using JavaScript. However, usage of the buttons provides users with only a few options to change the font size. Using an HTML slider allows users to choose a font size from within a wide range thus giving users more options to choose from. So, apart from buttons, we are also going to achieve the same feature using an HTML slider.
Approach:
- Define the <div> tag consisting the <p> tag, slider & 3 buttons.
- Make a JavaScript function to change the font size of the content in the div section. Use OnClick() event for the button click & for moving the slider, use OnChange() event.
- In the case of a button click, use the DOM to access the <div> tag for changing the value of the font-size attribute from javascript itself.
- In the case of moving the slider, again use DOM to access the value of the slider that has been set by the user and use this value as the font-size value for the <div> tag.
We will follow the above approach to build the font size controller & will make it stepwise manner.
Step 1: Create a simple HTML page with three buttons, a div consisting of a paragraph, and a slider. We are going to change the font size of this div content using the buttons or the slider. We will apply only the essential CSS stylings.
Step 2: We will write a JavaScript function to change the font size of the div when the user clicks the button or moves the slider. This change can be observed by using JavaScript events. Make use of the onClick() event to observe if the user has clicked the button and make use of the onChange() event to sense if the user has moved the slider. Create two functions for the two triggers events (ie. onClick and onChange).
HTML
<!DOCTYPE html> <html> <body> <center> <h1 style="color: green">GeeksForGeeks</h1> <button type="button" name="btn1">-A</button> <button type="button" name="btn2">A</button> <button type="button" name="btn3">A+</button> <br /><br /> <div style="padding: 20px; margin: 50px; font-size: 20px; border: 5px solid green;" id="container" class="container"> <p> A Computer Science portal for neveropen. It contains well written, well thought and well explained computer ming science and programarticles,quizzes and practice/ competitive programming/company interview questions. </p> </div> <input type="range" min="10" max="30" id="slider" value="20" /> </center> </body> </html> |
Javascript
var cont = document.getElementById("container"); function changeSizeByBtn(size) { // Set value of the parameter as fontSize cont.style.fontSize = size; } function changeSizeBySlider() { var slider = document.getElementById("slider"); // Set slider value as fontSize cont.style.fontSize = slider.value; } |
Output: Click here to see live code output
changing font size using JavaScript
