此示例代码允许您在Android的外部根目录中创建文件夹，在iOS中创建文档文件夹：

function writeFile() {
        if (sessionStorage.platform.toLowerCase() == "android") {
            window.resolveLocalFileSystemURL(cordova.file.externalRootDirectory, onFileSystemSuccess, onError);
        } else {
            window.requestFileSystem(LocalFileSystem.PERSISTENT, 0, onFileSystemSuccess, onError);
        }
}    

function onError(e) {
    alert("onError");
};

function onFileSystemSuccess(fileSystem) {
    var entry = "";
    if (sessionStorage.platform.toLowerCase() == "android") {
        entry = fileSystem;
    } else {
        entry = fileSystem.root;
    }
    entry.getDirectory("Folder_Name", {
        create: true,
        exclusive: false
    }, onGetDirectorySuccess, onGetDirectoryFail);
};

function onGetDirectorySuccess(dir) {
    dir.getFile(filename, {
        create: true,
        exclusive: false
    }, gotFileEntry, errorHandler);
};

function gotFileEntry(fileEntry) {
    // logic to write file in respective directory
};

function errorHandler(e) {
    // handle error
}