I have saved a JSON file in my local system and created a JavaScript file in order to read the JSON file and print data out. Here is the JSON file:
{"resource":"A","literals":["B","C","D"]}
Let’s say this is the path of the JSON file: /Users/Documents/workspace/test.json.
Could anyone please help me write a simple piece of code to read the JSON file and print the data in JavaScript?
This question is related to
javascript
json
The answer is
Since you have a web application, you may have a client and a server.
If you have only your browser, and you want to read a local file from a javascript that is running in your browser, that means that you have only a client. For security reasons, the browser should not let you do such thing.
However, as lauhub explained above, this seems to work:
http://www.html5rocks.com/en/tutorials/file/dndfiles/
Other solution is to setup somewhere in your machine a web server (tiny in windows or monkey in linux) and with an XMLHttpRequest or D3 library, request the file from the server and read it. The server will fetch the file from the local filesystem, and serve it to you through the web.
All the solutions above mentioned will work only when you have a local webserver running on your local host. If you want to achieve this with out a web server, you might need to put in some manual effort by uploading the JSON file using file upload control. The browser will not offer this functionality with out a local server because of security risks.
You can parse the uploaded file with out a local webserver as well. Here is the sample code I have achieved a solution similar problem.
<div id="content">
<input type="file" name="inputfile" id="inputfile">
<br>
<h2>
<pre id="output"></pre>
</h2>
</div>
<script type="text/javascript">
document.getElementById('inputfile')
.addEventListener('change', function () {
let fileReader = new FileReader();
fileReader.onload = function () {
let parsedJSON = JSON.parse(fileReader.result);
console.log(parsedJSON);
// your code to consume the json
}
fileReader.readAsText(this.files[0]);
})
</script>
In my case I want to read a local JSON file and show it in a html file on my desktop, that's all I have to do.
Note: Don't try to automate the file uploading using JavaScript, even that's also not allowed due the same security restrictions imposed by browsers.
You can use d3.js to import JSON files. Just call d3 on your html body:
<script src="https://d3js.org/d3.v5.min.js"></script>
Then put this on your js scripts:
d3.json("test.json").then(function(data_json) {
//do your stuff
})
If you could run a local web server (as Chris P suggested above), and if you could use jQuery, you could try http://api.jquery.com/jQuery.getJSON/
You could use D3 to handle the callback, and load the local JSON file data.json, as follows:
<script src="//d3js.org/d3.v3.min.js" charset="utf-8"></script>
<script>
d3.json("data.json", function(error, data) {
if (error)
throw error;
console.log(data);
});
</script>
Using the Fetch API is the easiest solution:
fetch("test.json")
.then(response => response.json())
.then(json => console.log(json));
It works perfect in Firefox, but in Chrome you have to customize security setting.
If you are using local files, why not just packade the data as a js object?
data.js
MyData = { resource:"A",literals:["B","C","D"]}
No XMLHttpRequests, no parsing, just use MyData.resource directly
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"}]';
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="javascrip.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);
For more information, see this reference.
You must create a new XMLHttpRequest instance and load the contents of the json file.
This tip work for me (https://codepen.io/KryptoniteDove/post/load-json-file-locally-using-pure-javascript):
function loadJSON(callback) {
var xobj = new XMLHttpRequest();
xobj.overrideMimeType("application/json");
xobj.open('GET', 'my_data.json', true); // Replace 'my_data' with the path to your file
xobj.onreadystatechange = function () {
if (xobj.readyState == 4 && xobj.status == "200") {
// Required use of an anonymous callback as .open will NOT return a value but simply returns undefined in asynchronous mode
callback(xobj.responseText);
}
};
xobj.send(null);
}
loadJSON(function(response) {
// Parse JSON string into object
var actual_JSON = JSON.parse(response);
});
You can import It like ES6 module;
import data from "/Users/Documents/workspace/test.json"
I took Stano's excellent answer and wrapped it in a promise. This might be useful if you don't have an option like node or webpack to fall back on to load a json file from the file system:
// wrapped XMLHttpRequest in a promise
const readFileP = (file, options = {method:'get'}) =>
new Promise((resolve, reject) => {
let request = new XMLHttpRequest();
request.onload = resolve;
request.onerror = reject;
request.overrideMimeType("application/json");
request.open(options.method, file, true);
request.onreadystatechange = () => {
if (request.readyState === 4 && request.status === "200") {
resolve(request.responseText);
}
};
request.send(null);
});
You can call it like this:
readFileP('<path to file>')
.then(d => {
'<do something with the response data in d.srcElement.response>'
});
Depending on your browser, you may access to your local files. But this may not work for all the users of your app.
To do this, you can try the instructions from here: http://www.html5rocks.com/en/tutorials/file/dndfiles/
Once your file is loaded, you can retrieve the data using:
var jsonData = JSON.parse(theTextContentOfMyFile);
Very simple.
Rename your json file to ".js" instead ".json".
<script type="text/javascript" src="my_json.js"></script>
So follow your code normally.
<script type="text/javascript">
var obj = JSON.parse(contacts);
However, just for information, the content my json it's looks like the snip below.
contacts='[{"name":"bla bla", "email":bla bla, "address":"bla bla"}]';
As many people mentioned before, this doesn't work using an AJAX call. However, there's a way around it. Using the input element, you can select your file.
The file selected (.json) need to have this structure:
[
{"key": "value"},
{"key2": "value2"},
...
{"keyn": "valuen"},
]
<input type="file" id="get_the_file">
Then you can read the file using JS with FileReader():
document.getElementById("get_the_file").addEventListener("change", function() {
var file_to_read = document.getElementById("get_the_file").files[0];
var fileread = new FileReader();
fileread.onload = function(e) {
var content = e.target.result;
// console.log(content);
var intern = JSON.parse(content); // Array of Objects.
console.log(intern); // You can index every object
};
fileread.readAsText(file_to_read);
});
You can use XMLHttpRequest() method:
var xmlhttp = new XMLHttpRequest();
xmlhttp.onreadystatechange = function() {
if (this.readyState == 4 && this.status == 200) {
var myObj = JSON.parse(this.responseText);
//console.log("Json parsed data is: " + JSON.stringify(myObj));
}
};
xmlhttp.open("GET", "your_file_name.json", true);
xmlhttp.send();
You can see the response of myObj using console.log statement(commented out).
If you know AngularJS, you can use $http:
MyController.$inject = ['myService'];
function MyController(myService){
var promise = myService.getJsonFileContents();
promise.then(function (response) {
var results = response.data;
console.log("The JSON response is: " + JSON.stringify(results));
})
.catch(function (error) {
console.log("Something went wrong.");
});
}
myService.$inject = ['$http'];
function myService($http){
var service = this;
service.getJsonFileContents = function () {
var response = $http({
method: "GET",
url: ("your_file_name.json")
});
return response;
};
}
If you have the file in a different folder, mention the complete path instead of filename.
I liked what Stano/Meetar commented above. I use it to read .json files. I have expanded their examples using Promise. Here is the plunker for the same. https://plnkr.co/edit/PaNhe1XizWZ7C0r3ZVQx?p=preview
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("DATA.json", function(text){
// var data = JSON.parse(text);
// console.log(data);
// });
var task1 = function (){
return new Promise (function(resolve, reject){
readTextFile("DATA.json", function(text){
var data = JSON.parse(text);
console.log('task1 called');
console.log(data);
resolve('task1 came back');
});
});
};
var task2 = function (){
return new Promise (function(resolve, reject){
readTextFile("DATA2.json", function(text){
var data2 = JSON.parse(text);
console.log('task2 called');
console.log(data2);
resolve('task2 came back');
});
});
}
Promise.race([task1(), task2()])
.then(function(fromResolve){
console.log(fromResolve);
});
The reading of JSON can be moved into another function, for DRY; but the example here is more of showcasing how to use promises.
Just use $.getJSON and then $.each to iterate the pair Key /value. Content example for the JSON file and functional code:
{
{
"key": "INFO",
"value": "This is an example."
}
}
var url = "file.json";
$.getJSON(url, function (data) {
$.each(data, function (key, model) {
if (model.key == "INFO") {
console.log(model.value)
}
})
});
- First, create a json file. In this example my file is words.json
[{"name":"ay","id":"533"},_x000D_
{"name":"kiy","id":"33"},_x000D_
{"name":"iy","id":"33"},_x000D_
{"name":"iy","id":"3"},_x000D_
{"name":"kiy","id":"35"},_x000D_
{"name":"kiy","id":"34"}]- And here is my code i.e,node.js. Note the
'utf8'argument toreadFileSync: this makes it return not aBuffer(althoughJSON.parsecan handle it), but a string. I am creating a server to see the result...
var fs=require('fs');_x000D_
var data=fs.readFileSync('words.json', 'utf8');_x000D_
var words=JSON.parse(data);_x000D_
var bodyparser=require('body-parser');_x000D_
console.log(words);_x000D_
var express=require('express');_x000D_
_x000D_
var app=express();_x000D_
_x000D_
var server=app.listen(3030,listening);_x000D_
_x000D_
function listening(){_x000D_
console.log("listening..");_x000D_
}_x000D_
app.use(express.static('website'));_x000D_
app.use(bodyparser.urlencoded({extended:false}));_x000D_
app.use(bodyparser.json());- When you want to read particular id details you can mention the code as..
app.get('/get/:id',function(req,res){_x000D_
_x000D_
var i;_x000D_
_x000D_
for(i=0;i<words.length;++i)_x000D_
{_x000D_
if(words[i].id==req.params.id){_x000D_
res.send(words[i]);_x000D_
}_x000D_
}_x000D_
console.log("success");_x000D_
_x000D_
});- When you entered in url as
localhost:3030/get/33it will give the details related to that id....and you read by name also. My json file has simillar names with this code you can get one name details....and it didn't print all the simillar names
app.get('/get/:name',function(req,res){_x000D_
_x000D_
var i;_x000D_
_x000D_
for(i=0;i<words.length;++i)_x000D_
{_x000D_
if(words[i].id==req.params.name){_x000D_
res.send(words[i]);_x000D_
}_x000D_
}_x000D_
console.log("success");_x000D_
_x000D_
});- And if you want to read simillar name details, you can use this code.
app.get('/get/name/:name',function(req,res){_x000D_
word = words.filter(function(val){_x000D_
return val.name === req.params.name;_x000D_
});_x000D_
res.send(word);_x000D_
_x000D_
console.log("success");_x000D_
_x000D_
});- If you want to read all the information in the file then use this code below.
app.get('/all',sendAll);_x000D_
_x000D_
function sendAll(request,response){_x000D_
response.send(words);_x000D_
_x000D_
}_x000D_
When in Node.js or when using require.js in the browser, you can simply do:
let json = require('/Users/Documents/workspace/test.json');
console.log(json, 'the json obj');
Do note: the file is loaded once, subsequent calls will use the cache.
One simple workaround is to put your JSON file inside a locally running server. for that from the terminal go to your project folder and start the local server on some port number e.g 8181
python -m SimpleHTTPServer 8181
Then browsing to http://localhost:8181/ should display all of your files including the JSON. Remember to install python if you don't already have.
The loading of a .json file from harddisk 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 works also for loading a .html or .txt files, by overriding the mime type parameter to "text/html", "text/plain" etc.
So, if you are planning to go with "Apache Tomcat" for hosting your JSON file,
1> After starting up the server, verify that your Apache Tomcat is up and running by going to this url: "localhost:8080" -
2> Next, go to the "webapps" folder - "C:\Program Files\Apache Software Foundation\Tomcat 8.5\webapps". And, create a project folder or copy your project folder.
3> Paste your json file over there.
4> And that's it. You are done! Just go to - "http://localhost:8080/$project_name$/$jsonFile_name$.json"
Source: Stackoverflow.com