javascript-for-in-loop/forInLoop.html at master · jovton/javascript-for-in-loop · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
<!DOCTYPE html>
<html>
<head>
    <link rel="stylesheet" type="text/css" href="css/forInLoop.css" />
    <script src="http://code.jquery.com/jquery-2.2.4.min.js"></script>
    <script src="js/forInLoop.js"></script>
</head>
<body>
    <h1>
        Understanding literal objects and arrays in "for in" loops.
    </h1>
    <p>
        Given...
    </p>
    <div class="visualize">
        <div class="code">
            <pre>

    function printValues(thing) {
        console.clear();

        for (var value in thing)
        {
            console.log(value);
            console.log(thing[value]);
        }
    }

            </pre>
        </div>
    </div>


    <p style="text-decoration: underline; color: blue;" onclick="jovton.printValues(person, this);">
        What does a person object with simple properties contain?
    </p>
    <div class="visualize">
        <div class="code">
            <pre>
    var person = {
        name: "Veronica",
        age: 35,
        height:"1.6 meters",
        sex: "female"
    }

    printValues(person);
            </pre>
        </div>
        <div class="console">
            <textarea>
            </textarea>
        </div>
    </div>


    <p style="text-decoration: underline; color: blue;" onclick="jovton.printValues(arrayWithObjects, this);">
        What does an array of objects with just one property contain?
    </p>
    <div class="visualize">
        <div class="code">
            <pre>

    var arrayWithObjects = [];

    arrayWithObjects.push({name: "Veronica"});
    arrayWithObjects.push({age: 36});
    arrayWithObjects.push({height: "1.4 meters"});
    arrayWithObjects.push({sex: "yes please!"});

    printValues(arrayWithObjects);

            </pre>
        </div>
        <div class="console">
            <textarea>
            </textarea>
        </div>
    </div>
    <p style="text-decoration: underline; color: blue;" onclick="jovton.printValues(arrayOfSimpleValues, this);">
        What does an array of simple values contain?
    </p>
    <div class="visualize">
        <div class="code">
            <pre>
    var arrayOfSimpleValues = [];

    arrayOfSimpleValues.push("name");
    arrayOfSimpleValues.push("Veronica");
    arrayOfSimpleValues.push("age");
    arrayOfSimpleValues.push(34);
    arrayOfSimpleValues.push("height");
    arrayOfSimpleValues.push("1.4 meters");
    arrayOfSimpleValues.push("sex")
    arrayOfSimpleValues.push("female");

    printValues(arrayOfSimpleValues);
            </pre>
        </div>
        <div class="console">
            <textarea>
            </textarea>
        </div>
    </div>


    <p>
        <strong>
            Moral of the story?
        </strong>
    </p>
    <p style="margin-bottom: 100px;">
        Use <code style="font-style:italic;"> for (int i=0; i < theArray.length; i++) </code> to iterate over an array, but <code style="font-style:italic;"> for (var property in object) </code> to iterate over an object's properties.
    </p>
</body>
</html>