parseCombinedPropertyStr.js

parseCombinedPropertyStr

/** 简易属性解释
 @param object 访问对象
 @param propertyStr 访问属性字符串，仅限于包含若干.或[]的组合，如"p1.p2[3][4].p5"
 @param [newValue] 如果不为undefined，则执行 object.propertyStr = newValue
 @return value of object.propertyStr if newValue !== undefined
 */
function parseCombinedPropertyStr(object, propertyStr, newValue) {
    if (!propertyStr) {
        return undefined;
    }

    var fields = propertyStr.split(".");

    var fieldValue = object;
    var fieldParentValue = object;
    var lastFieldName = undefined;

    function getFieldValue(object, field) {
        if (!object || !field) {
            throw new Error("invalid property str: " + propertyStr);
        }

        fieldParentValue = object;
        lastFieldName = field;
        return object[field];
    }

    for (var i = 0; i < fields.length; ++i) {
        var field = fields[i];
        var bracketStartPos = field.indexOf("[");
        if (bracketStartPos >= 0) {
            var remainPart = field.substring(bracketStartPos + 1);
            field = field.substring(0, bracketStartPos);

            fieldValue = getFieldValue(fieldValue, field);

            var indexStr = "";
            var j = 0;
            do {
                var indexStartPos = j;
                while (j < remainPart.length && remainPart[j] !== "]") {
                    ++j;
                }

                if (remainPart[j] === "]") {
                    indexStr = remainPart.substring(indexStartPos, j);

                    fieldValue = getFieldValue(fieldValue, indexStr);

                    if (j === remainPart.length - 1) {
                        break;
                    } else {
                        if (remainPart[j+1] === "[") {
                            j = j + 2;
                            if (j >= remainPart.length) {
                                throw new Error("invalid property str: " + propertyStr);
                            }
                        } else {
                            throw new Error("invalid property str: " + propertyStr);
                        }
                    }
                } else {
                    throw new Error("invalid property str: " + propertyStr);
                }
            } while (j < remainPart.length);
        } else {
            fieldValue = getFieldValue(fieldValue, field);
        }
    }

    if (newValue !== undefined) {
        fieldParentValue[lastFieldName] = newValue;
    } else {
        return fieldValue;
    }
}