Convert the plain object node to javascript object

@inner
@param {Object} node the plain object node
@param {Object} path the node path
@param {Object} t the babel type definition
@return {Object}
function getPlainObjectNodeValue(node, path, t) {
    let result;
    if (t.isObjectExpression(node)) {
        result = {};

        let props = node.properties || [];
        for (let i = 0, len = props.length; i < len; i++) {
            let subNode = props[i];
            let keyNode = subNode.key;
            let key;
            if (t.isLiteral(keyNode)) {
                key = keyNode.value;
            }
            else if (t.isIdentifier(keyNode)) {
                key = keyNode.name;
            }

            if (!key) {
                continue;
            }

            result[key] = getPlainObjectNodeValue(subNode.value, path, t);
        }
    }
    else if (t.isArrayExpression(node)) {
        result = [];
        node.elements.forEach(item => {
            result.push(getPlainObjectNodeValue(item, path, t));
        });
    }
    else if (t.isNullLiteral(node)) {
        result = null;
    }
    else if (t.isLiteral(node)) {
        result = node.value;
    }
    else {
        throw path.buildCodeFrameError('only constant is supported');
    }
    return result;
}