I am working with the following JSON string:
var j = { "name": "John" };
alert(j.length);
When I run this code, it alerts 'undefined'. How can I find the length of a JSON array object?
Thank you.
I am working with the following JSON string:
var j = { "name": "John" };
alert(j.length);
When I run this code, it alerts 'undefined'. How can I find the length of a JSON array object?
Thank you.
Begin by examining the json string:
var jsonData = '{"name":"John"}';
You can easily determine its length like this:
alert("The string contains "+jsonData.length+" characters"); // will display 15
Next, parse it into an object:
var jsonObj = JSON.parse(jsonData);
A Object in JavaScript behaves differently from an Array and does not have a length property. To find out how many properties it contains, you must count them:
var propertyNames = Object.keys(jsonObj);
alert("There are "+propertyNames.length+" properties in the object"); // will show 1
If your environment does not support the use of Object.keys to get an array of property names from an object, you will need to count manually:
var totalProps = 0;
for (var key in jsonObj) {
/* additional check only required if there are enumerable properties inherited
from a prototype */
totalProps++;
}
alert("Found "+totalProps+" properties after iteration"); // will alert 1
An alternative approach is to utilize the newer JSON.stringify function, which returns a string object that can be accessed using the length property:
var y = JSON.stringify({ "name" : "Jane" });
alert(y.length);
function calculateObjectProperties(object) {
let count = 0;
for (let key in object) {
if (object.hasOwnProperty(key)) {
count++;
}
}
return count;
}
let person = { "firstName": "Alice", "lastName": "Smith" };
alert(calculateObjectProperties(person)); // Output: 2
In JavaScript, there is no specific JSON Array object. The variable j is simply an object in JavaScript.
If you are looking to count the number of properties that an object has (excluding the prototype's properties), you can do so using the following method:
var propertyCount = 0;
for (var key in j) {
if (j.hasOwnProperty(key)) {
propertyCount++;
}
}
alert(propertyCount);
A different way to do it using Jquery:
var myObject = {"jsonObj" : [
{
"content" : [
{"name" : "John"},
]
}
]
}
$.each(myObject.jsonObj, function() {
alert(this.content.length);
});
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