Parse JSON in JavaScript? - Stack Overflow
javascript - How to read a json object in js - Stack Overflow
How to read an external local JSON file in JavaScript? - Stack Overflow
How to read an external JSON file as a string in javascript? - Stack Overflow
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The standard way to parse JSON in JavaScript is JSON.parse()
The JSON API was introduced with ES5 (2011) and has since been implemented in >99% of browsers by market share, and Node.js. Its usage is simple:
const json = '{ "fruit": "pineapple", "fingers": 10 }';
const obj = JSON.parse(json);
console.log(obj.fruit, obj.fingers);The only time you won't be able to use JSON.parse() is if you are programming for an ancient browser, such as IE 7 (2006), IE 6 (2001), Firefox 3 (2008), Safari 3.x (2009), etc. Alternatively, you may be in an esoteric JavaScript environment that doesn't include the standard APIs. In these cases, use json2.js, the reference implementation of JSON written by Douglas Crockford, the inventor of JSON. That library will provide an implementation of JSON.parse().
When processing extremely large JSON files, JSON.parse() may choke because of its synchronous nature and design. To resolve this, the JSON website recommends third-party libraries such as Oboe.js and clarinet, which provide streaming JSON parsing.
jQuery once had a $.parseJSON() function, but it was deprecated with jQuery 3.0. In any case, for a long time, it was nothing more than a wrapper around JSON.parse().
WARNING!
This answer stems from an ancient era of JavaScript programming during which there was no builtin way to parse JSON. The advice given here is no longer applicable and probably dangerous. From a modern perspective, parsing JSON by involving jQuery or calling eval() is nonsense. Unless you need to support IE 7 or Firefox 3.0, the correct way to parse JSON is JSON.parse().
First of all, you have to make sure that the JSON code is valid.
After that, I would recommend using a JavaScript library such as jQuery or Prototype if you can because these things are handled well in those libraries.
On the other hand, if you don't want to use a library and you can vouch for the validity of the JSON object, I would simply wrap the string in an anonymous function and use the eval function.
This is not recommended if you are getting the JSON object from another source that isn't absolutely trusted because the eval function allows for renegade code if you will.
Here is an example of using the eval function:
var strJSON = '{"result":true,"count":1}';
var objJSON = eval("(function(){return " + strJSON + ";})()");
alert(objJSON.result);
alert(objJSON.count);
If you control what browser is being used or you are not worried people with an older browser, you can always use the JSON.parse method.
This is really the ideal solution for the future.
First you need to parse the JSON string into JavaScript object, and then access the required property:
var obj = JSON.parse(json);
console.log(obj[0]["portal.home"]);
In older browsers which do not have native JSON support, you should use something like Crockford's json2.js, which will give you one; please don't use eval() on JSON, as it can lead to pretty bad things all around.
Use $.parseJSON (or JSON.parse in modern browsers) to convert your string into a Javascript object:
var json = '[{"portal.home":"Home"},{"displaytag.tracking.id":"Item ID"},{"displaytag.tracking.itemName":"Item Name"},{"displaytag.tracking.itemType":"Type"}]';
var object = $.parseJSON(json);
In your case your JSON string will create an array, so you will need to get the object at the correct index:
var portalHomeValue = object[0]["portal.home"];
For reading the external Local JSON file (data.json) using javascript, first create your data.json file:
data = '[{"name" : "Ashwin", "age" : "20"},{"name" : "Abhinandan", "age" : "20"}]';
Then,
Mention the path of the json file in the script source along with the javascript file
<script type="text/javascript" src="data.json"></script> <script type="text/javascript" src="javascript.js"></script>Get the Object from the json file
var mydata = JSON.parse(data); alert(mydata[0].name); alert(mydata[0].age); alert(mydata[1].name); alert(mydata[1].age);
The loading of a .json file from a hard disk is an asynchronous operation, and thus it needs to specify a callback function to execute after the file is loaded.
function readTextFile(file, callback) {
var rawFile = new XMLHttpRequest();
rawFile.overrideMimeType("application/json");
rawFile.open("GET", file, true);
rawFile.onreadystatechange = function() {
if (rawFile.readyState === 4 && rawFile.status == "200") {
callback(rawFile.responseText);
}
}
rawFile.send(null);
}
//usage:
readTextFile("/Users/Documents/workspace/test.json", function(text){
var data = JSON.parse(text);
console.log(data);
});
This function also works for loading a .html or .txt files, by overriding the mime type parameter to "text/html", "text/plain", etc.
You can use raw-loader to read a file as string:
var jsonString = require('raw-loader!constants/myfile.json');
var obj1 = JSON.parse(jsonString);
var obj2 = JSON.parse(jsonString);
You'll want to read the file contents first using a blob perhaps. Get the text content, then use the JSON.parse(jsonString).