How to reliably hash JavaScript objects?

Question

Is there a reliable way to JSON.stringify a JavaScript object that guarantees that the ceated JSON string is the same across all browsers, node.js and so on, given that the Java

Answer 1

After trying some hash algorithms and JSON-to-string methods, I found this to work the best (Sorry, it is typescript, can of course be rewritten to javascript):

// From: https://stackoverflow.com/questions/5467129/sort-javascript-object-by-key
function sortObjectKeys(obj){
    if(obj == null || obj == undefined){
        return obj;
    }
    if(typeof obj != 'object'){ // it is a primitive: number/string (in an array)
        return obj;
    }
    return Object.keys(obj).sort().reduce((acc,key)=>{
        if (Array.isArray(obj[key])){
            acc[key]=obj[key].map(sortObjectKeys);
        }
        else if (typeof obj[key] === 'object'){
            acc[key]=sortObjectKeys(obj[key]);
        }
        else{
            acc[key]=obj[key];
        }
        return acc;
    },{});
}
let xxhash64_ObjectToUniqueStringNoWhiteSpace = function(Obj : any)
{
    let SortedObject : any = sortObjectKeys(Obj);
    let jsonstring = JSON.stringify(SortedObject, function(k, v) { return v === undefined ? "undef" : v; });

    // Remove all whitespace
    let jsonstringNoWhitespace :string = jsonstring.replace(/\s+/g, '');

    let JSONBuffer: Buffer = Buffer.from(jsonstringNoWhitespace,'binary');   // encoding: encoding to use, optional.  Default is 'utf8'
    return xxhash.hash64(JSONBuffer, 0xCAFEBABE, "hex");
}

It used npm module: https://cyan4973.github.io/xxHash/ , https://www.npmjs.com/package/xxhash

The benefits:

• This is deterministic
• Ignores key order (preserves array order)
• Cross platform (if you can find equivalents for JSON-stringify) JSON-stringify will hopefully will not get a different implementation and the whitespace removal will hopefully make it JSON-formatting independent.
• 64-bit
• Hexadecimal string a result
• Fastest (0.021 ms for 2177 B JSON, 2.64 ms for 150 kB JSON)