array of objects javascript

1//Creating a list
2var fruits = ["Apple", "Banana", "Cherry"];
3
4//Creating an empty list
5var books = [];
6
7//Getting element of list
8//Lists are ordered using indexes
9//The first element in an list has an index of 0, 
10//the second an index of 1,
11//the third an index of 2,
12//and so on.
13console.log(fruits[0]) //This prints the first element 
14//in the list fruits, which in this case is "Apple"
15
16//Adding to lists
17fruits.push("Orange") //This will add orange to the end of the list "fruits"
18fruits[1]="Blueberry" //The second element will be changed to Blueberry
19
20//Removing from lists
21fruits.splice(0, 1) //This will remove the first element,
22//in this case Apple, from the list
23fruits.splice(0, 2) //Will remove first and second element
24//Splice goes from index of first argument to index of second argument (excluding second argument)

1//create an array like so:
2var colors = ["red","blue","green"];
3
4//you can loop through an array like this:
5for (var i = 0; i < colors.length; i++) {
6    console.log(colors[i]);
7}

1var widgetTemplats = [
2    {
3        name: 'compass',
4        LocX: 35,
5        LocY: 312
6    },
7    {
8        name: 'another',
9        LocX: 52,
10        LocY: 32
11    }
12]

1let fruits = ['Apple', 'Banana']
2
3console.log(fruits.length)
4// 2
5

1var events = [
2  {
3    userId: 1,
4    place: "Wormholes Allow Information to Escape Black Holes",
5    name: "Check out this recent discovery about workholes",
6    date: "2020-06-26T17:58:57.776Z",
7    id: 1
8  },
9  {
10    userId: 1,
11    place: "Wormholes Allow Information to Escape Black Holes",
12    name: "Check out this recent discovery about workholes",
13    date: "2020-06-26T17:58:57.776Z",
14    id: 2
15  },
16  {
17    userId: 1,
18    place: "Wormholes Allow Information to Escape Black Holes",
19    name: "Check out this recent discovery about workholes",
20    date: "2020-06-26T17:58:57.776Z",
21    id: 3
22  }
23];
24console.log(events[0].place);

1// The user object will be the test data for the notes taken below, 
2// ALL NOTE ARE AND INFO CAN BE FOUND AT HACKERNOON! 
3// THIS IS NOT MY WORK, I AM ONLY POSTING IT TO GREPPER FOR EASE OF USE OF FINDING THIS 
4// MATERIAL LATER IF NEED BE!
5// With that said enjoy the notes :D
6
7
8const user = {    
9  id: 101,    
10  email: 'jack@dev.com',    
11  personalInfo: {        
12    name: 'Jack',        
13    address: {            
14      line1: 'westwish st',            
15      line2: 'washmasher',            
16      city: 'wallas',            
17      state: 'WX'        
18    }    
19  }
20}
21
22// To access the name of our user we will write:
23const name = user.personalInfo.name;
24const userCity = user.personalInfo.address.city;
25
26// This is the easy and straight-forward approach
27
28// But for some reason, if our user's personal info is not available, the object structure 
29// will be like this:
30const user = {
31  id: 101,
32  email: 'jack@dev.com'
33}
34
35// Now if you try to access the name, you will be thrown "Cannot read property 'name' 
36// of undefined"
37const name = user.personalInfo.name; // Cannot read property 'name' of undefined
38
39//This is because we are trying to access the name key from an object that does not exist
40
41// The usual way how most devs deal with this scenario is
42const name = user && user.personalInfo ? user.personalInfo.name : null;
43// Undefined error will NOT be thrown as we check for existence before access
44
45// This is okay if your nested structure is simple, but if you have your data nested 
46// 5 or 6 levels deep, then your code will look really messy like this:
47
48let city;
49if (    
50  data && data.user && data.user.personalInfo &&    
51  data.user.personalInfo.addressDetails &&    
52  data.user.personalInfo.addressDetails.primaryAddress   
53  ) {    
54    city = data.user.personalInfo.addressDetails.primaryAddress;
55}
56
57// for more information please visit:
58// https://hackernoon.com/accessing-nested-objects-in-javascript-f02f1bd6387f