x-query-string/decode.js

var util = require('./util/util');
var isArray = util.isArray;

/**
 * Decode the URI Component encoded query string to object
 *
 * @param {string} The URI Component encoded query string
 * @returns {Object.<string, string>} Returns the decoded object
 */
function decode(string) {
    var object = {};
    var cache = {};
    var keyValueArray;
    var index;
    var length;
    var keyValue;
    var key;
    var value;

    // do not decode empty string or something that is not string
    if (string && typeof string === 'string') {
        keyValueArray = string.split('&');
        index = 0;
        length = keyValueArray.length;

        while (index < length) {
            keyValue = keyValueArray[index].split('=');
            key = decodeURIComponent(keyValue[0]);
            value = keyValue[1];

            if (typeof value === 'string') {
                value = decodeURIComponent(value);
            } else {
                value = null;
            }

            decodeKey(object, cache, key, value);

            index += 1;
        }
    }

    return object;
}

/**
 * Decode the specefied key
 *
 * @param {Object.<string, string>} object The object to hold the decoded data
 * @param {Object.<string, *>} cache The object to hold cache data
 * @param {string} key The key name to decode
 * @param {any} value The value to decode
 */
function decodeKey(object, cache, key, value) {
    var rBracket = /\[([^\[]*?)?\]$/;
    var rIndex = /(^0$)|(^[1-9]\d*$)/;
    var indexOrKeyOrEmpty;
    var parentKey;
    var arrayOrObject;
    var keyIsIndex;
    var keyIsEmpty;
    var valueIsInArray;
    var dataArray;
    var length;

    // check whether key is something like `person[name]` or `colors[]` or
    // `colors[1]`
    if ( rBracket.test(key) ) {
        indexOrKeyOrEmpty = RegExp.$1;
        parentKey = key.replace(rBracket, '');
        arrayOrObject = cache[parentKey];

        keyIsIndex = rIndex.test(indexOrKeyOrEmpty);
        keyIsEmpty = indexOrKeyOrEmpty === '';
        valueIsInArray = keyIsIndex || keyIsEmpty;

        if (arrayOrObject) {
            // convert the array to object
            if ( (! valueIsInArray) && isArray(arrayOrObject) ) {
                dataArray = arrayOrObject;
                length = dataArray.length;
                arrayOrObject = {};

                while (length--) {
                    if (arrayOrObject[length] !== undefined) {
                        arrayOrObject[length] = dataArray[length];
                    }
                }
            }
        } else {
            arrayOrObject = valueIsInArray ? [] : {};
        }

        if ( keyIsEmpty && isArray(arrayOrObject) ) {
            arrayOrObject.push(value);
        } else {
            // arrayOrObject is array or object here
            arrayOrObject[indexOrKeyOrEmpty] = value;
        }

        cache[parentKey] = arrayOrObject;

        decodeKey(object, cache, parentKey, arrayOrObject);
    } else {
        object[key] = value;
    }
}

module.exports = decode;