Example 1: Using split() and pop()
// program to get the file extension
function getFileExtension(filename){
// get file extension
const extension = filename.split('.').pop();
return extension;
}
// passing the filename
const result1 = getFileExtension('module.js');
console.log(result1);
const result2 = getFileExtension('module.txt');
console.log(result2);
Output
js txt
In the above program, 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. - The last array element, which is the extension, is returned using the
pop()
method.
Example 2: Using substring() and lastIndexOf()
// program to get the file extension
function getFileExtension(filename){
// get file extension
const extension = filename.substring(filename.lastIndexOf('.') + 1, filename.length);
return extension;
}
const result1 = getFileExtension('module.js');
console.log(result1);
const result2 = getFileExtension('test.txt');
console.log(result2);
Output
js txt
In the above program, 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.
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