CODEWITHSUNDEEP
javascriptbrowser
speedy
speedy

Reputation: 139

how to convert object to binary string

Here is how I compress binary string (char codes above 255) with pako:

var charData = xhr.responseText.split('').map(function(x){return x.charCodeAt(0);});
var binData = new Uint8Array(charData);
var data = pako.deflate(binData, {level:"9"});

Here is how I decompress data back:

var data2 = pako.inflate(xhr.responseText);

Now, how can I get original string in JavaScript from this object? I tried methods like this:

A.

pako.inflate(xhr.responseText, {to:"string"});

B.

String.fromCharCode.apply(null, data2);

C.

for (var i = 0, l = data2.length; i < l; i++)
{
result += String.fromCharCode(parseInt(array[i], 2));
}

All of these methods bring different data as JavaScript string than original. When I save decompressed pako.inflate(xhr.responseText) to a file (using functions with a.download) then dempressed file has exactly the same bytes as original file (so compression and decompression works correctly, without any byte modification).

Upvotes: 7

Views: 10814

Answers (3)

Stefnotch
Stefnotch

Reputation: 712

Don't use charCodeAt and fromCharCode for this task, since they will fail if you have Unicode in your string.

For example, the following breaks the emojis.

// Encode
var charData = "cat 🐈 dog 🐕".split('').map(function(x){return x.charCodeAt(0);});
var array = new Uint8Array(charData);

// Decode
var result = "";
for (var i = 0; i < array.length; i++)
{
  result += String.fromCharCode(array[i]);
}

Why? Because Javascript strings are stored as UTF-16, which leads to some characters being a pair of characters.

Instead, just use TextEncoder and TextDecoder, like @Ugur Abbasov recommended.

// Encode
const encoder = new TextEncoder();
const text = "your string goes here";
const binData = encoder.encode(text);
const compressedData = pako.deflate(binData, {level:"9"});

// Decode
const decoder = new TextDecoder();
const data2 = pako.inflate(compressedData);
const text2 = decoder.decode(data2);

Upvotes: 0

Ugur Abbasov
Ugur Abbasov

Reputation: 39

It isnt that hard. So just call class TextEncoder() and then encode method. For example

new TextEncoder().encode(JSON.stringify('Your object'))

For decode use just method decode.

Upvotes: 3

Pulkit Aggarwal
Pulkit Aggarwal

Reputation: 2672

I am just trying to do the same and found a way to convert Object to binary string and vice versa. I just create a two function that converts JSON Object to Binary String and Binary String to JSON Object viz. covertObjectToBinary and convertBinaryToObject. 

let obj = {a:1}
function covertObjectToBinary(obj) {
    let output = '',
        input = JSON.stringify(obj) // convert the json to string.
    // loop over the string and convert each charater to binary string.
    for (i = 0; i < input.length; i++) {
        output += input[i].charCodeAt(0).toString(2) + " ";
    }
    return output.trimEnd();
}

function convertBinaryToObject(str) {
    var newBin = str.split(" ");
    var binCode = [];
    for (i = 0; i < newBin.length; i++) {
        binCode.push(String.fromCharCode(parseInt(newBin[i], 2)));
    }
    let jsonString = binCode.join("");
    return JSON.parse(jsonString)
}
console.log('covertObjectToBinary =>', covertObjectToBinary(obj))
console.log('convertBinaryToObject =>', convertBinaryToObject(covertObjectToBinary(obj)))

Upvotes: 2

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