JavaScript Program to Get File Extension

JavaScript is a potent programming language that has gained immense popularity over the years, primarily as a result of its capacity to generate dynamic web pages. JavaScript's ability to manipulate files on the client-side is one of its essential capabilities. This article will discuss a JavaScript program that uses a file extension.

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Program to Get File Extension Using split() and pop()

In the code given below, the extension of the filename is extracted using the split() method and the pop() method.

• The filename is split into individual array elements using the split() method.
  Here, filename.split('.') gives ["module", "js"] by splitting the string. And also ["module", "txt"].
• Now, the pop() method is used to return the last array element used in the extension.

// JavaScript Program to get the file extension

function getFileExtension(filename){

    // extension of file
    const extension = filename.split('.').pop();
    return extension;
}
// passing the filename
const res1 = getFileExtension('module.js');
console.log(res1);

const res2 = getFileExtension('module.txt');
console.log(res2);

js
txt

Program to Get File Extension Using substring() and lastIndexOf()

In the code given below, the extension of the filename is extracted using the substring() method and the lastIndexOf() method.

• filename.lastIndexOf('.') + 1 returns the last position of . in the filename. 1 is added because the position count starts from 0.
• The filename.length property returns the length of the string.
• substring(filename.lastIndexOf('.') + 1, filename.length) method returns characters between the given indexes. For example, 'module.js'.substring(8, 10) returns js.
• The OR || operator is used to return the original string if there is no . in the filename.

// JavaScript Program to get the file extension

function getFileExtension(filename){
    // get file extension
    const extension = filename.substring(filename.lastIndexOf('.') + 1, filename.length);
    return extension;
}

const res1 = getFileExtension('module.js');
console.log(res1);

const res2 = getFileExtension('test.txt');
console.log(res2);

js
txt

Conclusion

This article concludes with a discussion of a JavaScript programme that uses a hook to extract the file extension from a filename. Using the aforementioned techniques, you can generate code that is easily maintained and reduces the likelihood of errors.