How to generate zip file using Buffer contents in node.js using JSZip?

Question

I have an array of strings which should be written to a .txt file. Also I need to compress the resulting .txt file to .zip format using JSZip. At the client side, I was able to generate a 'text/plain' Blob using this array of strings and then I compressed this Blob to .zip format using JSZip. I need to do the same on the server side using node.js, but I realized that Blob is not available in node.js. I tried using 'Buffer' instead of Blob, and I got a binary file compressed as .zip; I am a beginner with node.js and couldn't understand the concepts of Buffer. Can I create a Blob in node.js? or Can I perform the same operations with node.js Buffer?

At the client side I can generate the zip file from Blob contents like this,

//stringsArray is an array of strings
var blob = new Blob( stringsArray, { type: "text/plain" } );

var zip = new JSZip();
zip.file( 'file.txt' , blob );

zip.generateAsync( { type: 'blob', compression: 'DEFLATE' } )
.then( function( zipFile ){ 

    //do something with zipFile 

}, function( error ){ 

    console.log( 'Error in compression' );

} );

How can I do the same using Node.js?

Allomorph

This code should run as is. Perhaps check the documentation for JSZip if they have a different method for Node. – Unfriendly

@BrahmaDev , I got 'Blob is not defined' error in node.js – Allomorph

Sorry for that, you'd have to use Buffer. The documentation would be a good point to research around this : stuk.github.io/jszip/documentation/api_jszip/… – Unfriendly

Answer 1

I found a solution for this. In my code, I wasn't using the proper method to convert the array of strings to node.js buffer ( I wasn't able to compress the buffer using JSZip because the buffer was incorrect ). I tried the following code but it gave me an incorrect buffer,

//stringsArray is an array of strings
var buffer = Buffer.from( stringsArray );

The proper way is that, we have to convert each string to buffer first and then create a new buffer by appending all these sub buffers. I have created a custom buffer builder which will build a node.js buffer by appending strings to it. Following is the new method I have tried, and it worked for me.

var CustomBufferBuilder = function() {

    this.parts = [];
    this.totalLength = 0;

}

CustomBufferBuilder.prototype.append = function( part ) {

    var tempBuffer = Buffer.from( part );
    this.parts.push( tempBuffer );
    this.totalLength += tempBuffer.length;
    this.buffer = undefined;

};

CustomBufferBuilder.prototype.getBuffer = function() {

    if ( !this.buffer ) {

       this.buffer = Buffer.concat( this.parts, this.totalLength );

    }
    return this.buffer;

};


var customBufferBuilder = new CustomBufferBuilder();
var stringsArray = [ 'hello ', 'world.', '\nThis ', 'is', ' a ', 'test.' ];//stringsArray is an array of strings
var len = stringsArray.length;
for( var i = 0; i< len; i++ ){

    customBufferBuilder.append( stringsArray[ i ] );

}

var bufferContent = customBufferBuilder.getBuffer();

var zip = new JSZip();
zip.file( 'test.txt', bufferContent, { binary : true } );
zip.generateAsync( { type : "nodebuffer", compression: 'DEFLATE' } )
.then( function callback( buffer ) {

    fs.writeFile( 'test.zip', buffer, function( err ){

        if( err ){

            //tasks to perform in case of error

        }
        else{

            //other logic

        }

    } );

}, function( e ) {

    //tasks to perform in case of error

} );

As output, I got the zip file( test.zip ) and test.txt inside it. The test.txt file inside the zip file contains the following words, 'hello world.\nThis is a test.'.

Thanks @BrahmaDev for spending time to look into my question :)

Allomorph