Syntax

Example:

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{ "name": "Johnson", "age": 28, "site": null }

JSON objects are written using curly braces {…}. They can contain multiple key/value pairs.

Keys must be strings, while values can be any valid JSON data type (string, number, object, array, boolean, or null). Keys and values are separated by colons (:), and each key/value pair is separated by commas (,).

Accessing Object Values

You can use dot (.) notation to access object values:

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var teacher = { "name": "Johnson", "age": 28, "site": null };
var x = teacher.name;
console.log(x); // Output: Johnson

Alternatively, you can use square brackets ([]):
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var teacher = { "name": "Johnson", "age": 28, "site": null };
var x = teacher["name"];
console.log(x); // Output: Johnson

Looping Through Objects

Use a for…in loop to iterate over object properties:

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var teacher = { "name": "Johnson", "age": 28, "site": null };
for (var x in teacher) {
    console.log(x);
}
// Output:
// name
// age
// site

To access property values while looping, use square brackets:
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var teacher = { "name": "Johnson", "age": 28, "site": null };
for (var x in teacher) {
    console.log(teacher[x]);
}
// Output:
// Johnson
// 28
// null

Nested JSON Objects

JSON objects can contain other JSON objects:

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var teacher = {
    "name": "Johnson",
    "age": 28,
    "site": {
        "site1": "www.linjiangxiong.com",
        "site2": "m.linjiangxiong.com",
        "site3": "blog.linjiangxiong.com"
    }
};

Access nested objects using dot notation or square brackets:
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var x = teacher.site.site1;
// or
var x = teacher.site["site1"];

Executing console.log(x); will output www.linjiangxiong.com.

Modifying Values

Use dot notation or square brackets to modify JSON object values:

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teacher.site.site1 = "https://www.linjiangxiong.com/";
// or
teacher.site["site1"] = "https://www.linjiangxiong.com/";

Deleting Object Properties

Use the delete keyword to remove JSON object properties:

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delete teacher.site.site1;
// or
delete teacher.site["site1"];

For example, perform the following code.
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var teacher = {
    "name": "Johnson",
    "age": 28,
    "site": {
        "site1": "www.linjiangxiong.com",
        "site2": "m.linjiangxiong.com",
        "site3": "blog.linjiangxiong.com"
    }
};

delete teacher.site.site1;

console.log(teacher);

The output will be:
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{
  "name": "Johnson",
  "age": 28,
  "site": {
    "site2": "m.linjiangxiong.com",
    "site3": "blog.linjiangxiong.com"
  }
}