Cannot read property 'push' of undefined in AngularJS - angularjs

Question

I have a factory that calls 4 json files and then I want to do some treatmenet for each data from these files and push them into an array of objects this is the code I wrote :
myapp.factory('wordsCloudFactory', function($http) {
var factory = {
getList: function() {
return $http.get('data/periode_1_file.JSON')
.then(function(response1) {
return $http.get('data/periode_2_file.JSON')
.then(function(response2) {
return $http.get('data/periode_3_file.JSON')
.then(function(response3) {
return $http.get('data/periode_4_file.JSON')
.then(function(response4) {
var words = [{
'period1': [],
'period2': [],
'period3': [],
'period4': []
}];
console.log(words);
for (var i = response1.data['X_id'].length - 1; i >= 0; i--) {
words['period1'].push({
id: response.data['X_id'][i],
count: response.data['count'][i]
});
};
for (var i = response2.data['X_id'].length - 1; i >= 0; i--) {
words['period2'].push({
id: response.data['X_id'][i],
count: response.data['count'][i]
});
};
for (var i = response3.data['X_id'].length - 1; i >= 0; i--) {
words['period3'].push({
id: response.data['X_id'][i],
count: response.data['count'][i]
});
};
for (var i = response4.data['X_id'].length - 1; i >= 0; i--) {
words['period4'].push({
id: response.data['X_id'][i],
count: response.data['count'][i]
});
};
return words;
}, function(error) {
return 'There was an error getting data';
})
}, function(error) {
return 'There was an error getting data';
})
}, function(error) {
return 'There was an error getting data';
})
}, function(error) {
return 'There was an error getting data';
})
}
};
return factory;
})
this code it doesnt work it shows me an error message : 'Cannot read property 'push' of undefined'.
How can I solve this ?
As you can see in my code there are a lot of nested $http.get methodes isn't there another way to write that ?

Answer 1

Your words is an array of object
var words = [{
'period1': [],
'period2': [],
'period3': [],
'period4': []
}];
You have to access it by index.
Try like this
words[0]['period1'].push({
id: response.data['X_id'][i],
count: response.data['count'][i]
});
JSFIDDLE
If it's just an object Like
var words = {
'period1': [],
'period2': [],
'period3': [],
'period4': []
};
Then your push was ok .
words['period1'].push({
id: response.data['X_id'][i],
count: response.data['count'][i]
});
JSFIDDLE