MapオブジェクトのJSON相互コンバーター(最適化済み)

01. mapReviver.js

function mapReviver(key, value){
	var len = key.length;
	if(len < 5) return value;
	if(key.charCodeAt(--len) !== 112) return value;
	if(key.charCodeAt(--len) !== 97)  return value;
	if(key.charCodeAt(--len) !== 109) return value;
	if(key.charCodeAt(--len) !== 36)  return value;
	
	this[key.slice(0, len)] = new Map(value);
}

02. mapReplacer.js

function mapReplacer(key, value){
	if(!value) return value;
	
	var type = typeof(value);
	
	if(type.length !== 6) return value;
	if(type.charCodeAt(0) !== 111) return value;
	if(type.charCodeAt(1) !== 98)  return value;
	if(type.charCodeAt(2) !== 106) return value;
	if(type.charCodeAt(3) !== 101) return value;
	if(type.charCodeAt(4) !== 99)  return value;;
	if(type.charCodeAt(5) !== 116) return value;
	
	if(value instanceof Date)  return value;
	if(value instanceof Array) return value;
	
	if(value instanceof Map) {
		var mapIterator = value.entries();
		var itrValue, output = [];
		
		while(true){
			itrValue = mapIterator.next();
			if(itrValue.done) break;
			
			output.push([itrValue.value[0], itrValue.value[1]]);
		}
		
		return output;
	}
	
	var replacer = Object.create(value);
	var keys = Object.keys(value);
	for(var i=0,iLen=keys.length,innerValue;i<iLen;++i){
		innerValue = value[keys[i]];
		if(!(innerValue instanceof Map)){
			replacer[keys[i]] = innerValue;
			continue;
		}
		
		replacer[keys[i]+"$map"] = innerValue;
	}
	
	return replacer;
}

03. index.js

var input = `{
	"arr":     [["key1", "value1"], ["key2", "value2"], ["key3", "value3"]],
	"map$map": [["key1", "value1"], ["key2", "value2"], ["key3", "value3"]]
}`;

var json = JSON.parse(input, mapReviver);
console.log("JSON String => JSON Object");
console.log(json);

var jsonStr = JSON.stringify(json, mapReplacer);
console.log("JSON Object => JSON String");
console.log(jsonStr);