jsonSerializer

import asdf;

import std.array;
import std.bigint;
import std.format: singleSpec;

auto app = appender!string;
auto ser = jsonSerializer(&app.put!(const(char)[]));
auto state0 = ser.structBegin;

    ser.putEscapedKey("null");
    ser.putValue(null);

    ser.putEscapedKey("array");
    auto state1 = ser.listBegin();
        ser.elemBegin; ser.putValue(null);
        ser.elemBegin; ser.putValue(123);
        ser.elemBegin; ser.putNumberValue(12300000.123, singleSpec("%.10e"));
        ser.elemBegin; ser.putValue("\t");
        ser.elemBegin; ser.putValue("\r");
        ser.elemBegin; ser.putValue("\n");
        ser.elemBegin; ser.putNumberValue(BigInt("1234567890"));
    ser.listEnd(state1);

ser.structEnd(state0);
ser.flush;

assert(app.data == `{"null":null,"array":[null,123,1.2300000123e+07,"\t","\r","\n",1234567890]}`);