Using Salesforce Apex and FileReader() and encodeURIComponent() from JavaScript, we can easily upload a file using Aura Component lightning:input of type file.

Sample Code:

Apex Class:

public class FileUploadController {
    
    @AuraEnabled
    public static String uploadFile(
        String filename, String base64Content
    ) {
        ContentVersion objContentVersion = new ContentVersion();
        base64Content = EncodingUtil.urlDecode(
            base64Content, 
            'UTF-8'
        );
        objContentVersion.VersionData = EncodingUtil.base64Decode( 
            base64Content 
        );
        objContentVersion.Title = filename;
        objContentVersion.PathOnClient = filename;
        try {
            
            insert objContentVersion;
            
        } catch( DMLException e ) {
            
            System.debug(
                'Error while uploading the file ' +
                e.getMessage()
            );
            return e.getMessage();
            
        }        
        ContentDocumentLink objContentDocumentLink = new ContentDocumentLink();
        objContentDocumentLink.ContentDocumentId = [
            SELECT ContentDocumentId 
            FROM ContentVersion 
            WHERE Id =: objContentVersion.Id
        ].ContentDocumentId;
        objContentDocumentLink.ShareType = 'V';
        try {
            
            insert objContentDocumentLink;
            
        } catch( DMLException e ) {
            
            System.debug(
                'Error while uploading the file ' +
                e.getMessage()
            );
            return e.getMessage();
            
        }
        
        return 'File Uploaded Successfully';
        
    }
    
}

Lightning Aura Component:

Component:

<aura:component 
                implements="force:appHostable" 
                controller="FileUploadController">
    <aura:attribute name="fileName" type="String"/>
    <lightning:card class="slds-p-around_x-small" title="Upload Section">
        <lightning:input 
                         label="Upload File/Attachment/Document"
                         type="file"
                         onchange="{!c.handleFileUpload}"
                         multiple="false"
                         aura:id="fileId"/>
        {!v.fileName}
        <aura:set attribute="footer">
            <lightning:button 
                              label="Upload"
                              onclick="{!c.submitFile}"/>
        </aura:set>
    </lightning:card>
</aura:component>

JavaScript Controller:

( {
    
    handleFileUpload : function( component, event, helper ) {
        
        let selectedFiles = component.find(
            "fileId"
        ).get(
            "v.files"
        );
        let selectedFile = selectedFiles[ 0 ];
        console.log(
            'File Name is',
            selectedFile.name
        );
        component.set(
            "v.fileName",
            selectedFile.name
        );
        console.log(
            'File Size is',
            selectedFile.size
        );
        
    },
    
    submitFile : function( component, event, helper ) {
        
        console.log(
            'Inside the Submit File'
        );
        let selectedFiles = component.find(
            "fileId"
        ).get(
            "v.files"
        );
        let selectedFile = selectedFiles[ 0 ]; 
        let objFileReader = new FileReader();    
        objFileReader.onload = $A.getCallback( function() {
            let fileContent = objFileReader.result;
            let base64 = 'base64,';
            let dataStart = fileContent.indexOf( base64 ) + base64.length; 
            fileContent = fileContent.substring( dataStart );
            helper.processFileUpload( component, fileContent, selectedFile );
        } ); 
        objFileReader.readAsDataURL(
            selectedFile
        );
        
    }
    
} )

JavaScript Helper:

({
    
    processFileUpload : function( component, fileContent, selectedFile ) {
                
        console.log(
            'Inside the Process File'
        );     
        console.log(
            'File Name is',
            selectedFile.name
        );
        console.log(
            'Encoded value is',
            encodeURIComponent( fileContent )
        );
        let action = component.get( "c.uploadFile" );
        console.log( 
            'Action for Upload File called'
        );
        action.setParams( {
            filename: selectedFile.name,
            base64Content: encodeURIComponent( fileContent )
        } );
        action.setCallback( this, function( response ) {
            
            let state = response.getState();
            console.log( 
                'State is',
                state
            );
            console.log(
                'Return Value is',
                response.getReturnValue()
            );
            
            if ( state === "SUCCESS" ) {
                
            	console.log( 
                    'Success' 
                );
                component.set(
                    "v.fileName",
                    "File Successfully Uploaded"
                );
                
            } else {
                
            	console.log( 
                    'Failed' 
                );
                component.set(
                    "v.fileName",
                    "File Upload Failed. Please try again."
                );
                
            }
            
		} );
        $A.enqueueAction( action );
        
    }
    
})

Output: