tinyzip.js - A tiny zip file generator in 70 lines of javascript.

zip.js

// Author: Raheman Vaiya
// License: WTFPL
//
// A tiny zip generator in < 70 lines of javascript.
// Produces an uncompressed zip blob when fed an array
// of the form:
//
// [{name: 'filename', data: <Uint8Array>}]
//
// Useful for bookmarklets, don't use this in production :P. 
//
// Less than 2% the size of minified jszip (without all the bells and whistles).
//
// Refs:
//
// https://en.wikipedia.org/wiki/ZIP_(file_format)
// https://gist.github.com/rvaiya/9b39813d74ce3d5e1412e6b813a29c3b#file-zip-implementation-go

function zip(files) {
		// Generate the crc32 table instead of hardcoding it to avoid having a giant constant
		// in the minified output...
		const crc32_table = function() {
				const tbl = [];
				var c;
				for(var n = 0; n < 256; n++){
						c = n;
						for(var k =0; k < 8; k++){
								c = ((c&1) ? (0xEDB88320 ^ (c >>> 1)) : (c >>> 1));
						}

						tbl[n] = c;
				}

				return tbl;
		}();

		function crc32(arr) {
				var crc = -1;
				for(var i=0; i<arr.length; i++) {
						crc = (crc >>> 8) ^ crc32_table[(crc ^ arr[i]) & 0xFF];
				}
				return (crc ^ (-1)) >>> 0;
		}

		function putUint32s(arr, offset, ...values) {
				const dv = new DataView(arr.buffer);
				values.forEach((v,i)=>dv.setUint32(offset+i*4, v, true));
		}

		function putUint16s(arr, offset, ...values) {
				const dv = new DataView(arr.buffer);
				values.forEach((v,i)=>dv.setUint16(offset+i*2, v, true));
		}


		const records = [];
		const te = new TextEncoder('utf8');

		var offset = 0;
		var cdSz = 0;

		files.forEach(file => {
				const fh = new Uint8Array(30+file.name.length);
				const fname = te.encode(file.name);
				const chksum = crc32(file.data);

				putUint32s(fh, 0, 0x04034b50);
				putUint32s(fh, 14, chksum, file.data.length, file.data.length);
				putUint16s(fh, 26, file.name.length);

				fh.set(fname, 30);

				file.header = fh;
				file.offset = offset;

				records.push(fh);
				records.push(file.data);

				//Create CD records pending flush at the end...
				file.cdr = new Uint8Array(46+file.name.length);

				putUint32s(file.cdr, 0, 0x02014b50);
				putUint32s(file.cdr, 16, chksum, file.data.length, file.data.length);
				putUint16s(file.cdr, 28, file.name.length);
				putUint32s(file.cdr, 42, offset);

				file.cdr.set(fname, 46);

				cdSz += file.cdr.length;
				offset += file.header.length + file.data.length;
		});

		//Push all accrued CD records..
		files.forEach(f=>records.push(f.cdr));
		
		//Add EOCD record...
		const eocd = new Uint8Array(22);

		putUint32s(eocd, 0, 0x06054b50);
		putUint16s(eocd, 8, files.length, files.length);
		putUint32s(eocd, 12, cdSz, offset);

		records.push(eocd);

		return new Blob(records, {type : 'application/zip'});
}

zip.min.js

function zip(k){function f(a,b,...d){const c=new DataView(a.buffer);d.forEach((e,g)=>c.setUint32(b+4*g,e,!0))}function n(a,b,...d){const c=new DataView(a.buffer);d.forEach((e,g)=>c.setUint16(b+2*g,e,!0))}const q=function(){const a=[];for(var b,d=0;256>d;d++){b=d;for(var c=0;8>c;c++)b=b&1?3988292384^b>>>1:b>>>1;a[d]=b}return a}(),h=[],r=new TextEncoder("utf8");var l=0,p=0;k.forEach(a=>{const b=new Uint8Array(30+a.name.length),d=r.encode(a.name);var c=a.data;for(var e=-1,g=0;g<c.length;g++)e=e>>>8^
q[(e^c[g])&255];c=(e^-1)>>>0;f(b,0,67324752);f(b,14,c,a.data.length,a.data.length);n(b,26,a.name.length);b.set(d,30);a.header=b;a.offset=l;h.push(b);h.push(a.data);a.cdr=new Uint8Array(46+a.name.length);f(a.cdr,0,33639248);f(a.cdr,16,c,a.data.length,a.data.length);n(a.cdr,28,a.name.length);f(a.cdr,42,l);a.cdr.set(d,46);p+=a.cdr.length;l+=a.header.length+a.data.length});k.forEach(a=>h.push(a.cdr));const m=new Uint8Array(22);f(m,0,101010256);n(m,8,k.length,k.length);f(m,12,p,l);h.push(m);return new Blob(h,
{type:"application/zip"})};