How to Convert JSON String to JSON Object in JavaScript

You can use the JSON.parse() method in JavaScript, to convert a JSON string into a JSON object. JSON is a commonly used data format for exchanging data between a server and web applications. It can be used in a variety of ways and today I am sharing an example here, which shows how to convert a JSON string data to a JSON object in JavaScript.

I recently used this method to update this demo page, where I have a <pre> element with data in JSON format and I wanted to read the data in my JavaScript code. However, to read the data from the element, which is a string, I had to convert the string first to a JSON object.

Here’s how I did it.

<html>
<head>
    <title>Convert JSON String to JSON Object in JavaScript</title>
</head>
<body>
    <pre id="jsonData"
        style="border:solid 1px #CCC;padding:0 5px;">
[
    {
        "ID": "001",
        "Name": "Eurasian Collared-Dove",
        "Type": "Dove",
        "Scientific Name": "Streptopelia"
    },
  
	{
        "ID": "002",
        "Name": "Bald Eagle",
        "Type": "Hawk",
        "Scientific Name": "Haliaeetus leucocephalus" 
    },

	{
        "ID": "003",
        "Name": "Cooper's Hawk",
        "Type": "Hawk",
        "Scientific Name": "Accipiter cooperii"  
    }
]
    </pre>

    <p>
        <input type="button" id="btClick" value="String to JSON" onclick="str2json()" />
    </p>
    <p>Note: See the output in your browsers console window!</p>
</body>
<script>
    function str2json() {
        var str = document.getElementById('jsonData').innerHTML;
        var jsonObj = JSON.parse(str);
        console.log(jsonObj);
    }
</script>
</html>

Try it

The data inside the <pre> element is in JSON format (a string). Using the innerHTML property, I am extracting the data from the element and storing it in a string variable.

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To use the data that I have extracted from the <pre> element, I have to convert it into a JSON object. So, I am using the method JSON.parse(). The parameter inside the method has the string data.

When you run above code, the console window will show an output like this …

Using JSON.parse method to Convert JSON String into a JSON Object

The method has converted the JSON string to a JSON object.

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Now you can use the object’s data for a variety of purposes, such as, convert the JSON data to an HTML table or populate a SELECT dropdown list with the JSON, etc.

Run a simple for loop to read the data inside the object. For example, if I want to parse (or read) the Name in the JSON, then I’ll do this,

for (i = 0; i < jsonObj.length; i++) {
    console.log(jsonObj[i].Name);
}

Try it

Similarly, you can read other values in the JSON object.

Remember: The string must be in a correct JSON format. Or else, it will throw an error. JSON.parse() method does allow trailing commas (a string or a text that ends with a comma). The below string will throw an error, since it has , (comma) at the end.

"Scientific Name": "Haliaeetus leucocephalus",

That’s it. Thanks for reading. ☺

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How to Convert JSON String to JSON Object in JavaScript

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