如何在JavaScript中获取数组格式？

Question

I am getting an array in AngularJs with factory function. This is the console

Array[0]
  0: "value1"
  1: "value2"
  length:2

But when i want to get the length of the array

console.log(array.length)

getting data from mysql in loopback

 app.factory("getFoo", function(Communications){
 return {
   getCommi: function(val,id){
    var array = [];
    var myVals = Communications.find({
                    filter: {
                        where: {
                            and : [{
                                communications_type_code : val
                            },{
                                object_id : id
                            }]
                        }
                    } 
                }, function(data){
                    for(var i=0; i< data.length; i++){
                        array[i] = data[i].contact_value;
                    }
                    return array;
        });

        return array;
      }
  }
});

The controller look like:

app.controller('usersFormCtrl', ['$scope','getFoo',function($scope,getFoo){
var emails = getFoo.getCommi(3,1);

setTimeout(function(){
    $scope.formModel.emails = [];
    for(var index=0; index < $scope.emails.length; index++){
        $scope.emails = emails;
    }
}, 0)
}])

I get that the length is 0. Why is that?

Answer 1

This is a timing issue. The first time you ask for the length it is indeed 0, but when you inspect the object a few seconds later with Chrome Dev Tools you are inspecting the live object which has now been filled.

You can confirm this by using setTimeout

setTimeout(function(){
   console.log(array);
}, 0)

You can checkout this link for further explanation

UPDATE

In angular, use $timeout instead of setTimeout . Like this:

$timeout(function(){
   console.log(array);
}, 0)

Answer 2

The length property of an Array in JavaScript is immutable. You can either set an Array's size by defining how many properties will be in there: var a = new Array(2), or by just passing in your values: var a = ['value1', 'value2'].

Answer 3

You mix async with sync approaches here.

Communications.find is async but you use it in getCommi like sync function.

When you call getCommi the function return immediately with empty array .

Please change according below.

app.factory("getFoo", function(Communications){
 return {
   getCommi: function(val,id, cb){
    var array = [];
    var myVals = Communications.find({
                    filter: {
                        where: {
                            and : [{
                                communications_type_code : val
                            },{
                                object_id : id
                            }]
                        }
                    } 
                }, function(data){
                    for(var i=0; i< data.length; i++){
                        array[i] = data[i].contact_value;
                    }
                    cb(null, array);
        });   
      }
  }
});

and

app.controller('usersFormCtrl', ['$scope','getFoo',function($scope,getFoo){
getFoo.getCommi(3,1, function(err, emails){
  $scope.formModel.emails = [];
    for(var index=0; index < $scope.emails.length; index++){
        $scope.emails = emails;
    }
});    
}])

DISCLAIMER : I don't know angular.

Answer 4

尝试这个，

console.log(array[0].length)