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How to change the font weight of text using JavaScript?

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Aug 24, 2023 pm 11:45 PM

如何使用 JavaScript 更改文本的字体粗细？

Using JavaScript is one of the most well-known ways to change the font weight of any text on a web page. We can build interactive applications using JavaScript and HTML elements. Font weight refers to the thickness of the characters. In this article, we will learn how to change the font weight of text using JavaScript.

Using the style fontWeight attribute

Let’s see how to change the font weight of a single element, such as a paragraph or heading. To do this we will use the "style.fontWeight" property of the element. This property is an object that contains all CSS properties and their corresponding values.

grammar

We can use the following syntax to change the font weight of the text -

document.getElementById("myId").style.fontWeight = "normal|lighter|bold|bolder|value|initial|inherit"

Here we can specify "normal", "lighter", "bold", "bold" or a value between 100 and 900 for the fontWeight property.

Therefore, we can assign a value to the fontWeight property in two ways, namely numbers and keywords.

Example: Assign Number to fontWeight property

To use this method to change the font-weight of an HTML element, the number should be set between 100 and 900. Let’s look at an example of using numbers to change the font weight of a title element.

<html>
<body>
   <h2 id="Change-Font-Weight-of-HTML-Element-in-JavaScript">Change Font Weight of HTML Element in JavaScript</h2>
   <button onclick="myfuction()">Click to change font weight to 300</button>
   <script>
      function myfuction(){
         const heading = document.getElementById("myHeading");
         heading.style.fontWeight = 300;
      }
   </script>
</body>
</html>

As we can see in the example, here we use the getElementById method to select the heading element with the ID "myHeading" and then set the font-weight property of the object to 300, we will set the text of the object to 300. The title element is lighter than normal.

Example: Assigning keywords to the fontWeight property

To change the font weight of an HTML element using this method, we can use Normal, Bold or Bold. Setting font-weight to normal corresponds to setting font-weight to 400, and setting font-weight to bold corresponds to setting font-weight to 700.

<html>
<body>
   <div id="myDiv">
      <p id="myParagraph">
         Change Font Weight of HTML Element using
      keywords Method
      </p>
   </div>
   <button onclick="myfuction()">Click to change font weight to bolder</button>
   <script>
      function myfuction(){
         const paragraph = document.getElementById("myParagraph");
         paragraph.style.fontWeight = "bolder";
      }
   </script>
</body>
</html>

As we can see in the example, here we use the getElementById method to select the paragraph element with the ID "myParagraph", and then set the font-weight property of the object to "bolder", which we set to " bolder" will make the paragraph element's text bolder than before.

Change the font weight of multiple elements

Suppose if you want to change the font weight of multiple elements at once, such as all paragraphs in a document, then we can use the "querySelectorAll" method. It returns a node list of all HTML elements that match the given CSS selector.

Example: Using forEach method

Let's look at an example of using the forEach method to change the font weight of all elements of a paragraph in the document.

<html>
<body>
   <div id="myDiv">
      <p>First Paragraph</p>
      <p>Second Paragraph</p>
   </div>
   <button onclick="myfuction()">Click to change font weight</button>
   <script>
      function myfuction() {
         const paragraphs = document.querySelectorAll("p");
         paragraphs.forEach(function(paragraph) {
            paragraph.style.fontWeight = 700;
         });
      }
   </script>
</body>
</html>

In the above example, we use "querySelectorAll" to select all elements of the paragraph in the HMTL document. We then use the forEach method of the node list to iterate over all paragraphs and set their font weight to 700.

The "forEach" method is a useful way to iterate over a list of nodes. It allows us to perform a function on each element in the list. In this example, we set the "fontWeight" property of each paragraph element's style object to 700.

Example: Using the for-of loop method

Let’s look at another example using the for-of loop method to change the font weight of multiple elements in the document. A for-of loop is a traditional method or another way to iterate over a list of nodes.

<html>
<body>
   <h3 id="Example-of-Font-Weight-Text-Changing-for-of-method">Example of Font-Weight Text Changing for-of method</h3>
   <div id="myDiv">
      <p>First Paragraph </p>
      <p>Second Paragraph</p>
   </div>
   <button onclick="myfuction()">Click to change font weight</button>
   <script>
      function myfuction() {
         const paragraphs = document.querySelectorAll("p");
         for (const paragraph of paragraphs) {
            paragraph.style.fontWeight = 700;
         }
      }
   </script>
</body>
</html>

In this example, we use a "for-of" loop to iterate over a paragraph and set its font weight to 700. The difference between for loop and for-of loop is that for-of loop allows us to directly access the elements of the node list, whereas in for loop we access its index.

in conclusion

In this article, we successfully demonstrated how to change the font weight of text with an example. Here we see different examples of using JavaScript to change the font weight of a single element and multiple elements. We have written two different examples using forEach method and for-of method for multiple elements.

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