[etc] fetch API+golang 파일 다운로드

javascript part

// http://url/filename.ext
function fileDownload(url) {
	
var fileName = url.split('/').pop()			

if (!url) {
	alert("No Notion Page");
	return false;
} else {
	return fetch(url, { method: 'GET' }).then( (resp) => {
		if (!resp|| !resp.ok) {
		  alert("Download Error");
		  return false;
		}
          
		return resp.blob();
    }).then(function(blob) {
		if(blob) {
            // use download.js
			download(blob, fileName);
		}   
    });
  }
}

download.js import

http://danml.com/js/download.js

html part

<input type="button" onclick="fileDownload('http://localhost:8100/static/axios.png')" value="Down!!!" />

golang part

아주 심플(?)하게 구현하였다.

package main

import (
	"net/http"
	"strings"
)

var orig = http.StripPrefix("/static/", http.FileServer(http.Dir("./upload")))
var wrapped = http.HandlerFunc(
	func(w http.ResponseWriter, r *http.Request) {

		if strings.HasSuffix(r.URL.Path, "/") {
			http.NotFound(w, r)
			return
		}

		w.Header().Set("Access-Control-Allow-Origin", "http://localhost")
		w.Header().Set("Access-Control-Allow-Methods", "GET")
		orig.ServeHTTP(w, r)
	})

func main() {
	http.Handle("/static/", wrapped)
	http.ListenAndServe(":8100", nil)
}

테스트

잘됨 ㄳ

download.js

혹시라도 문제가 생기면 내리겠음.

function download(data, strFileName, strMimeType) {
	
	var self = window, // this script is only for browsers anyway...
		u = "application/octet-stream", // this default mime also triggers iframe downloads
		m = strMimeType || u, 
		x = data,
		D = document,
		a = D.createElement("a"),
		z = function(a){return String(a);},
		
		
		B = self.Blob || self.MozBlob || self.WebKitBlob || z,
		BB = self.MSBlobBuilder || self.WebKitBlobBuilder || self.BlobBuilder,
		fn = strFileName || "download",
		blob, 
		b,
		ua,
		fr;

	if(String(this)==="true"){ 
		x=[x, m];
		m=x[0];
		x=x[1]; 
	}
	
	
	
	//go ahead and download dataURLs right away
	if(String(x).match(/^data\:[\w+\-]+\/[\w+\-]+[,;]/)){
		return navigator.msSaveBlob ?  // IE10 can't do a[download], only Blobs:
			navigator.msSaveBlob(d2b(x), fn) : 
			saver(x) ; // everyone else can save dataURLs un-processed
	}//end if dataURL passed?
	
	try{
	
		blob = x instanceof B ? 
			x : 
			new B([x], {type: m}) ;
	}catch(y){
		if(BB){
			b = new BB();
			b.append([x]);
			blob = b.getBlob(m); // the blob
		}
		
	}
	
	
	
	function d2b(u) {
		var p= u.split(/[:;,]/),
		t= p[1],
		dec= p[2] == "base64" ? atob : decodeURIComponent,
		bin= dec(p.pop()),
		mx= bin.length,
		i= 0,
		uia= new Uint8Array(mx);

		for(i;i<mx;++i) uia[i]= bin.charCodeAt(i);

		return new B([uia], {type: t});
	 }
	  
	function saver(url, winMode){
		
		
		if ('download' in a) { //html5 A[download] 			
			a.href = url;
			a.setAttribute("download", fn);
			a.innerHTML = "downloading...";
			D.body.appendChild(a);
			setTimeout(function() {
				a.click();
				D.body.removeChild(a);
				if(winMode===true){setTimeout(function(){ self.URL.revokeObjectURL(a.href);}, 250 );}
			}, 66);
			return true;
		}
		
		//do iframe dataURL download (old ch+FF):
		var f = D.createElement("iframe");
		D.body.appendChild(f);
		if(!winMode){ // force a mime that will download:
			url="data:"+url.replace(/^data:([\w\/\-\+]+)/, u);
		}
		 
	
		f.src = url;
		setTimeout(function(){ D.body.removeChild(f); }, 333);
		
	}//end saver 
		

	if (navigator.msSaveBlob) { // IE10+ : (has Blob, but not a[download] or URL)
		return navigator.msSaveBlob(blob, fn);
	} 	
	
	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===z ){
			try{
				return saver( "data:" +  m   + ";base64,"  +  self.btoa(blob)  ); 
			}catch(y){
				return saver( "data:" +  m   + "," + encodeURIComponent(blob)  ); 
			}
		}
		
		// Blob but not URL:
		fr=new FileReader();
		fr.onload=function(e){
			saver(this.result); 
		};
		fr.readAsDataURL(blob);
	}	
	return true;
} /* end download() */