HTML

17
Sep
2021

How to uncompress file inside ZIP archive using HTML5 & JSZip

In our previous post How to read local ZIP in HTML5/Javascript using JSZip we provided an example of how to use JSZip to list files inside a local ZIP archive using HTML5.

This post will expand upon this in order to read the content of a file compressed inside a local ZIP archive file.

In this example, we’ll read a local ZIP file using HTML5 <input type="file"> and uncompress its content. We’ll read the word/document.xml file, so you can upload any .docx file to test that.

JSZip.loadAsync(ev.target.result).then(function(zip) {
    zip.file("word/document.xml").async("ArrayBuffer").then(function(data) {
        // data is an ArrayBuffer
        // TODO Your code goes here!
    })
}).catch(function(err) {
    console.error("Failed to open", filename, " as ZIP file:", err);
})

Full example

<html>
<body>
    <input type="file" id="myfile" onchange="onMyfileChange(this)" />

    <script src="https://unpkg.com/[email protected]/dist/jszip.js" type="text/javascript"></script>
    <script type="text/javascript">
        function onMyfileChange(fileInput) {
            if(fileInput.files[0] == undefined) {
                return ;
            }

            var filename = fileInput.files[0].name;
            var reader = new FileReader();
            reader.onload = function(ev) {
                JSZip.loadAsync(ev.target.result).then(function(zip) {
                    zip.file("word/document.xml").async("ArrayBuffer").then(function(data) {
                        // data is an ArrayBuffer
                        // TODO Your code goes here!
                    })
                }).catch(function(err) {
                    console.error("Failed to open", filename, " as ZIP file:", err);
                })
            };
            reader.onerror = function(err) {
                console.error("Failed to read file", err);
            }
            reader.readAsArrayBuffer(fileInput.files[0]);
        }
    </script>
</body>
</html>

 

 

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Posted by Uli Köhler in HTML, Javascript
17
Sep
2021

How to include JSZip in the browser

The JSZip documentation doesn’t make it entirely clear how to include it in the browser, i.e. which <script> tag you need to use in order to load JSZip.

Here’s the appropriate <script> tag:

<script src="https://unpkg.com/[email protected]/dist/jszip.min.js" type="text/javascript"></script>

You can also use the non-minified version which does not have minified class and object names:

<script src="https://unpkg.com/[email protected]/dist/jszip.js" type="text/javascript"></script>

 

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Posted by Uli Köhler in HTML, Javascript
17
Sep
2021

How to read local ZIP in HTML5/Javascript using JSZip

In our previous post How to load local file in Javascript using HTML5 FileReader we showed how to read a local file using the HTML5 FileReader.

Based on this, it’s pretty easy to use JSZip to read a local ZIP file:

var reader = new FileReader();
reader.onload = function(ev) {
    JSZip.loadAsync(ev.target.result).then(function(zip) {
        // TODO Your code goes here. This is just an example.
        console.log(zip)
    }).catch(function(err) {
        console.error("Failed to open", filename, " as ZIP file:", err);
    })
};
reader.onerror = function(err) {
    console.error("Failed to read file", err);
}
reader.readAsArrayBuffer(fileInput.files[0]);

One example of what you can do using the JSZip object is to list the filenames inside the ZIP file:

var filename = fileInput.files[0].name;
var reader = new FileReader();
reader.onload = function(ev) {
    JSZip.loadAsync(ev.target.result).then(function(zip) {
        for(let [filename, file] of Object.entries(zip.files)) {
            console.log(filename);
        }
    }).catch(function(err) {
        console.error("Failed to open", filename, " as ZIP file:", err);
    })
};
reader.onerror = function(err) {
    console.error("Failed to read file", err);
}
reader.readAsArrayBuffer(fileInput.files[0]);

Full example

<html>
<body>
    <input type="file" id="myfile" onchange="onMyfileChange(this)" />

    <script src="https://unpkg.com/[email protected]/dist/jszip.js" type="text/javascript"></script>
    <script type="text/javascript">
        function onMyfileChange(fileInput) {
            if(fileInput.files[0] == undefined) {
                return ;
            }

            var filename = fileInput.files[0].name;
            // var filesize = fileInput.files[0].size;
            var reader = new FileReader();
            reader.onload = function(ev) {
                JSZip.loadAsync(ev.target.result).then(function(zip) {
                    console.log(zip)
                }).catch(function(err) {
                    console.error("Failed to open", filename, " as ZIP file");
                })
            };
            reader.onerror = function(err) {
                console.error("Failed to read file", err);
            }
            reader.readAsArrayBuffer(fileInput.files[0]);
        }
    </script>
</body>
</html>

 

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Posted by Uli Köhler in HTML, Javascript
17
Sep
2021

How to load local file in Javascript using HTML5 FileReader

In HTML5, you can not only upload a file to a server but also process it directly in the browser using Javascript.

This post provides minimal examples of how to use FileReader to do that.

How to read a text file

<html>
<body>
    <input type="file" id="myfile" onchange="onMyfileChange(this)" />
    <script type="text/javascript">
        function onMyfileChange(fileInput) {
            if(fileInput.files[0] == undefined) {
                return ;
            }

            // Example of what information you can read
            // var filename = fileInput.files[0].name;
            // var filesize = fileInput.files[0].size;
            var reader = new FileReader();
            reader.onload = function(ev) {
                var content = ev.target.result; // content is a string
                console.log("Successfully read file");
            };
            reader.onerror = function(err) {
                console.error("Failed to read file", err);
            }
            reader.readAsText(fileInput.files[0]);
        }
    </script>
</body>
</html>

How to read a binary file as ArrayBuffer

<html>
<body>
    <input type="file" id="myfile" onchange="onMyfileChange(this)" />
    <script type="text/javascript">
        function onMyfileChange(fileInput) {
            if(fileInput.files[0] == undefined) {
                return ;
            }

            // Example of what information you can read
            // var filename = fileInput.files[0].name;
            // var filesize = fileInput.files[0].size;
            var reader = new FileReader();
            reader.onload = function(ev) {
                var content = ev.target.result; // content is an ArrayBuffer object
                console.log("Successfully read file");
            };
            reader.onerror = function(err) {
                console.error("Failed to read file", err);
            }
            reader.readAsArrayBuffer(fileInput.files[0]);
        }
    </script>
</body>
</html>

 

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Posted by Uli Köhler in HTML, Javascript
02
Aug
2021

Minimal leaflet.js example with Stamen terrain tiles

This minimal self-contained HTML example can serve as a good starting point for your own leaflet application. Using Stamen Terrain tiles not only provides a nice view of the physical geography but has the added advantage of not requiring any API key.

<html>
    <head>
        <link rel="stylesheet" href="https://unpkg.com/[email protected]/dist/leaflet.css"
        integrity="sha512-xodZBNTC5n17Xt2atTPuE1HxjVMSvLVW9ocqUKLsCC5CXdbqCmblAshOMAS6/keqq/sMZMZ19scR4PsZChSR7A=="
        crossorigin=""/>
        <script src="https://unpkg.com/[email protected]/dist/leaflet.js"
        integrity="sha512-XQoYMqMTK8LvdxXYG3nZ448hOEQiglfqkJs1NOQV44cWnUrBc8PkAOcXy20w0vlaXaVUearIOBhiXZ5V3ynxwA=="
        crossorigin=""></script>
        <script type="text/javascript" src="https://stamen-maps.a.ssl.fastly.net/js/tile.stamen.js?v1.3.0"></script>
        <style>
            #mymap { height: 100%; }
        </style>
    </head>
    <body>
        <div id="mymap"></div>
        <script type="text/javascript">
            var layer = new L.StamenTileLayer("terrain");
            var map = new L.Map("mymap", {
                /* Center: Munich, Germany */
                center: new L.LatLng(48.1, 11.5),
                /* Show most of western Europe */
                zoom: 6
            });
            map.addLayer(layer);
        </script>
    </body>
</html>

Look and feel of the example:

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Posted by Uli Köhler in HTML, Javascript, Leaflet
15
Aug
2019

Pure Javascript equivalent to jQuery $(window).load()

The pure Javascript equivalent to

$(window).load(function() {
    // Your code goes here!

})

is

window.addEventListener("load", function() { 
    // Your code goes here!
});

Note that it’s not supported by IE8, but that should not be an issue in 2019.

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Posted by Uli Köhler in HTML, Javascript
05
Aug
2019

What is ‘&hellip;’ in HTML?

&hellip; is the HTML entity code for the ellipsis dots:

…

If you see it on a webpage outside the HTML source code, it usually means that the author or content management system has encoded the HTML entity incorrectly. You should only ever see … on the page except in literal HTML sourcecode.

I recommend using the unicode character HORIZONTAL ELLIPSIS (see the code block above) instead of the HTML entity &hellip;. Ensure that you have

<meta charset="utf-8" />

in your HTML <head> for compatibility.

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Posted by Uli Köhler in HTML