如果不知道索引，如何遍历2d数组

Question

My array looks like this:

var permissions = new Array();

permissions['role-1'] = new Array();
permissions['role-1']['permission-1'] = "perm1";
permissions['role-1']['permission-3'] = "perm3";
permissions['role-1']['permission-5'] = "perm5";
permissions['role-2']['permission-1'] = "perm1";
permissions['role-2']['permission-5'] = "perm5";

How would I loop through such an array and go through all the elements? I can't use for-loop since that would use integer indexes.

Answer 1

You are confusing arrays (which are best suited to integer-indexed properties) with objects (which are designed to use any valid string as a property name). Objects are sometimes called "associative arrays," which makes the distinction a bit confusing.

Instead of using new Array() , you should use the object literal shorthand to initialize your permissions variable. Then, you can use Object.keys to get a list of the keys you used to create your object and do something with your key-value pairs:

 var permissions = { 'role-1': { 'permission-1': 'perm1', 'permission-3': 'perm3', 'permission-4': 'perm1', 'permission-5': 'perm5', }, 'role-2': { 'permission-1': 'perm1', 'permission-5': 'perm5' } } var object = permissions['role-1'] Object.keys(object).forEach(function (key) { // Do something with your key-value pairs console.log(key, this[key]) }, object) 

For more information, see "How do I loop through or enumerate a JavaScript object?"

Answer 2

I would use an object to store that.

var permissions = {};
permissions['role-1'] = permissions['role-1'] || {};
permissions['role-1']['permission-1'] = "perm1";
permissions['role-1']['permission-3'] = "perm3";

Then you can iterate over the keys

for(var key in permissions)
   console.log(permissions[key]);