A module that shortens JSON to a number of bytes while keeping syntactically valid JSON. Useful for when apis can only accept a certain byte length for input. Only works for NODE but can be ported to browsers. WIP.

truncate-json.js

function getBytes(string) {
    return Buffer.byteLength(String(string), 'utf8');
}

function trimToBytes(string, diff) {
    return Buffer.alloc(diff, string, 'utf8').toString();
}

// This is only intended atm for flat objects with string values
// Does not handle edge cases
// Push each item / level onto stack
// reverse stack anf append opposite
function limitReplacer(maxBytes) {
    const size = 2; // {} or []
    const replacer = function (key, value) {
        if (size >= maxBytes) {
            return;
        }
        size += getBytes('"":,');
        if (!Array.isArray(this)) {
            size += getBytes(key);
        }
        const valBytes = getBytes(value);
        if (size + valBytes < maxBytes) {
            size += valBytes;
            return value;
        } else {
            const diff = maxBytes - size;
            const truncatedValue = trimToBytes(string, diff);
            size += diff;
            return truncatedValue;
        }
    }
    return replacer;
}

// problems to solve
// Object.keys() if value is object to determine if keys alone + 1 exceed limit
// Either raise if not all keys can be included even if every value is truncated, or start kicking off keys starting with the last

// test of different types
var foo = JSON.stringify({ a: 'foo', b: 5, c: 'hello', d: { e: 'f'}, g: [new String(1), Number(2), 3, Symbol(), new Boolean(0)] }, function(k, v) {
console.log( k, v, this, typeof v, Object.keys(v));
return v;
})