Node js - Node.js Parse JSON Little information to use JSON Data

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Node.js Parse JSON

Node.js Parse JSON – For parsing JSON data in Node.js, we can use JSON.parse() function of JavaScript Engine.

Little information to use JSON Data

key:value is the building block.
{ } contains an element.
[ ] contains an array of elements.
An element can have multiplekey:value pairs.
Value can be a simple value like number or string etc., or an element or an array.
Elements in an Array could be accessed using index
Multiplekey:value pairs or elements are separated by comma

A Simple Example Node.js JSON Parsing Program

Following example helps you to use JSON.parse() function and access the elements from JSON Object.

nodejs-parse-json.js
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// json data
var jsonData = '{"persons":[{"name":"John","city":"New York"},{"name":"Phil","city":"Ohio"}]}';
 
// parse json
var jsonParsed = JSON.parse(jsonData);
 
// access elements
console.log(jsonParsed.persons[0].name);

Terminal Output for running nodejs-parse-json.js
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arjun@arjun-VPCEH26EN:~/workspace/nodejs$ node nodejs-parse-json.js 
John

Example – Node.js Parse JSON File

We shall read a File containing JSON data to a variable and parse that data.

Consider following JSON File, sample.json

sample.json
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{
    "persons": [{
            "name": "John",
            "city": "Kochi",
            "phone": {
                "office": "040-528-1258",
                "home": "9952685471"
            }
 
        },
        {
            "name": "Phil",
            "city": "Varkazha",
            "phone": {
                "office": "040-528-8569",
                "home": "7955555472"
            }
        }
    ]
}

Node.js JSON File Parsing Program

nodejs-parse-json-file.js
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// include file system module
var fs = require('fs');
 
// read file sample.json file
fs.readFile('sample.json',
    // callback function that is called when reading file is done
    function(err, data) {        
        // json data
        var jsonData = data;
 
        // parse json
        var jsonParsed = JSON.parse(jsonData);
 
        // access elements
        console.log(jsonParsed.persons[0].name + "'s office phone number is " + jsonParsed.persons[0].phone.office);
        console.log(jsonParsed.persons[1].name + " is from " + jsonParsed.persons[0].city);
});

Run the above Node.js program.

Terminal output on running nodejs-parse-json-file.js
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arjun@arjun-VPCEH26EN:~/workspace/nodejs$ node nodejs-parse-json-file.js 
John's office phone number is 040-528-1258
Phil is from Kochi

Conclusion :

In this Node.js Tutorial – Node.js JSON File Parsing – we have learnt to parse JSON data from a variable or file using JSON.parse() function with the help of example Node.js programs.