How to send a long string with WebSocket

I had a problem with WebSocket when I try to send a long string(1688 Bytes in my case). I got error
"Execution Interrupted during event processing.
New interpreter error: LOW_MEMORY,MEMORY".

Then I modified the ws module, made the send function can accept a json object, to prevent string copy. But in another for loop, it still make a copy of source, I made comment down below.

g.prototype.send = function(a, b) {
    let c, f, d, e;
    try {
        if (
            ((c = a.value.length),
                125 < a.value.length && (c = 126),
                this.socket.write(
                    h(void 0 === b ? 129 : b, c + (this.masking ? 128 : 0))
                ),
                126 == c &&
                (this.socket.write(h(a.value.length >> 8)),
                    this.socket.write(h(a.value.length))),
                this.masking)
        ) {
            for (c = [], f = "", d = 0; 4 > d; d++) {
                (e = Math.floor(255 * Math.random())), (c[d] = e), (f += h(e));
            }
            for (d = 0; d < a.value.length; d++) {
                //here will make a copy of source
                f += h(a.value.charCodeAt(d) ^ c[3 & d]);
            }
            print(process.memory());
            this.socket.write(f);
        } else this.socket.write(a);//2
    } catch (e) {
        (c = d = f = e = null), this.initializeConnection();
    }
}

I tried 5 methods(like using flash as buffer or turn source string in to array at first and exchange char in it in for loop) to fix it ,but none of them work.

I wish to use the second method to send data, but server will emit error "MASK must be set".

Anyone know how to deal with this? Thank you.