Welcome folks today in this blog post we will be talking about a new javascript library called as download.js library which lets the user downloads the files such as images,pdf and videos from url as an attachment inside the browser.
Installation
Now to install this library there are various options available. If you want to use in the browser using javascript you can use the cdn link and include it inside the html as shown below
index.html
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<!doctype html> <html> <head> <meta charset="UTF-8"> <title>Download.js CDN Example in Browser</title> <script src='//js.zapjs.com/js/download.js'></script> </head> </html> |
The second option is to use at the node.js server side. You can install it as a module by executing the below command
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npm i downloadjs |
Third option is very simple you can create downloadfile.js and copy paste the entire code of the library which is shown below
downloadfile.js
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<script>//download.js v4.2, by dandavis; 2008-2016. [CCBY2] see http://danml.com/download.html for tests/usage // v1 landed a FF+Chrome compat way of downloading strings to local un-named files, upgraded to use a hidden frame and optional mime // v2 added named files via a[download], msSaveBlob, IE (10+) support, and window.URL support for larger+faster saves than dataURLs // v3 added dataURL and Blob Input, bind-toggle arity, and legacy dataURL fallback was improved with force-download mime and base64 support. 3.1 improved safari handling. // v4 adds AMD/UMD, commonJS, and plain browser support // v4.1 adds url download capability via solo URL argument (same domain/CORS only) // v4.2 adds semantic variable names, long (over 2MB) dataURL support, and hidden by default temp anchors // https://github.com/rndme/download (function (root, factory) { if (typeof define === 'function' && define.amd) { // AMD. Register as an anonymous module. define([], factory); } else if (typeof exports === 'object') { // Node. Does not work with strict CommonJS, but // only CommonJS-like environments that support module.exports, // like Node. module.exports = factory(); } else { // Browser globals (root is window) root.download = factory(); } }(this, function () { return function download(data, strFileName, strMimeType) { var self = window, // this script is only for browsers anyway... defaultMime = "application/octet-stream", // this default mime also triggers iframe downloads mimeType = strMimeType || defaultMime, payload = data, url = !strFileName && !strMimeType && payload, anchor = document.createElement("a"), toString = function(a){return String(a);}, myBlob = (self.Blob || self.MozBlob || self.WebKitBlob || toString), fileName = strFileName || "download", blob, reader; myBlob= myBlob.call ? myBlob.bind(self) : Blob ; if(String(this)==="true"){ //reverse arguments, allowing download.bind(true, "text/xml", "export.xml") to act as a callback payload=[payload, mimeType]; mimeType=payload[0]; payload=payload[1]; } if(url && url.length< 2048){ // if no filename and no mime, assume a url was passed as the only argument fileName = url.split("/").pop().split("?")[0]; anchor.href = url; // assign href prop to temp anchor if(anchor.href.indexOf(url) !== -1){ // if the browser determines that it's a potentially valid url path: var ajax=new XMLHttpRequest(); ajax.open( "GET", url, true); ajax.responseType = 'blob'; ajax.onload= function(e){ download(e.target.response, fileName, defaultMime); }; setTimeout(function(){ ajax.send();}, 0); // allows setting custom ajax headers using the return: return ajax; } // end if valid url? } // end if url? //go ahead and download dataURLs right away if(/^data\:[\w+\-]+\/[\w+\-]+[,;]/.test(payload)){ if(payload.length > (1024*1024*1.999) && myBlob !== toString ){ payload=dataUrlToBlob(payload); mimeType=payload.type || defaultMime; }else{ return navigator.msSaveBlob ? // IE10 can't do a[download], only Blobs: navigator.msSaveBlob(dataUrlToBlob(payload), fileName) : saver(payload) ; // everyone else can save dataURLs un-processed } }//end if dataURL passed? blob = payload instanceof myBlob ? payload : new myBlob([payload], {type: mimeType}) ; function dataUrlToBlob(strUrl) { var parts= strUrl.split(/[:;,]/), type= parts[1], decoder= parts[2] == "base64" ? atob : decodeURIComponent, binData= decoder( parts.pop() ), mx= binData.length, i= 0, uiArr= new Uint8Array(mx); for(i;i<mx;++i) uiArr[i]= binData.charCodeAt(i); return new myBlob([uiArr], {type: type}); } function saver(url, winMode){ if ('download' in anchor) { //html5 A[download] anchor.href = url; anchor.setAttribute("download", fileName); anchor.className = "download-js-link"; anchor.innerHTML = "downloading..."; anchor.style.display = "none"; document.body.appendChild(anchor); setTimeout(function() { anchor.click(); document.body.removeChild(anchor); if(winMode===true){setTimeout(function(){ self.URL.revokeObjectURL(anchor.href);}, 250 );} }, 66); return true; } // handle non-a[download] safari as best we can: if(/(Version)\/(\d+)\.(\d+)(?:\.(\d+))?.*Safari\//.test(navigator.userAgent)) { url=url.replace(/^data:([\w\/\-\+]+)/, defaultMime); if(!window.open(url)){ // popup blocked, offer direct download: if(confirm("Displaying New Document\n\nUse Save As... to download, then click back to return to this page.")){ location.href=url; } } return true; } //do iframe dataURL download (old ch+FF): var f = document.createElement("iframe"); document.body.appendChild(f); if(!winMode){ // force a mime that will download: url="data:"+url.replace(/^data:([\w\/\-\+]+)/, defaultMime); } f.src=url; setTimeout(function(){ document.body.removeChild(f); }, 333); }//end saver if (navigator.msSaveBlob) { // IE10+ : (has Blob, but not a[download] or URL) return navigator.msSaveBlob(blob, fileName); } if(self.URL){ // simple fast and modern way using Blob and URL: saver(self.URL.createObjectURL(blob), true); }else{ // handle non-Blob()+non-URL browsers: if(typeof blob === "string" || blob.constructor===toString ){ try{ return saver( "data:" + mimeType + ";base64," + self.btoa(blob) ); }catch(y){ return saver( "data:" + mimeType + "," + encodeURIComponent(blob) ); } } // Blob but not URL support: reader=new FileReader(); reader.onload=function(e){ saver(this.result); }; reader.readAsDataURL(blob); } return true; }; /* end download() */ }));</script> |
Usage
Now to use this library in an actual web application we will be using html and javascript So just create a index.html file and inside this file we have a simple input field where the user can enter the url of the file to be downloaded and a button to trigger the action.
index.html
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<!doctype html> <html> <head> <meta charset="UTF-8"> <title>Download Image Demo</title> <style> body { font: menu; } </style> <script src='//js.zapjs.com/js/download.js'></script> </head> <body> <h1>Download Image File Demo using download.js</h1> <input type="url" id="url" required/> <button id="download">Download</button> </body> </html> |
Now if you open the index.html file inside the browser you will see a input field where the user can enter the path of the file to be downloaded
Now we need to write the javascript code when we click the button what should happen
script.js
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document.getElementById('download').addEventListener('click',(e) => { let url = document.getElementById('url').value downloadFile(url) }) function downloadFile(url){ var x = new XMLHttpRequest(); x.open("GET", url, true); x.responseType = 'blob'; x.onload = function (e) { // the name of the file and mime type can be skipped download(x.response, "dlBinAjax.png", "image/png"); } x.send(); } |
So here guys we are also using some ajax to initiate the request to download the image and then we are using the download library method passing the url and the actual file name and the extension of the file in this case it is png image file.
Now if you click the button a png image file will be downloaded as an attachment as shown below in the picture
