After receiving a string st from a web service, I convert it into an object. How can I determine the number of arrays inside this object? In this particular case, there are 2 arrays.
var st = "{[{"Name": "fake", "Address": "add"]},[{"Name": "fake", "Address": "add"}]}";
var json = eval(st);
The statement json.length consistently shows a value of 1.
@user123 I have made some modifications to your JSON structure. Hopefully, this will prove to be helpful.
var people = {
"person1": {
"Name": "Adam",
"Address": "USA"
},
"person2": {
"Name": "Jamie",
"Address": "USA"
}
};
var count = 0;
// var count = people.length; // This won't work
for (property in people) { // This should return 2
if (people.hasOwnProperty(property)) {
count++;
}
}
It's interesting that `json.length` is giving a result; the JSON string seems to be incorrect. The main curly braces (`{}`) indicate an object, which should have keys and values, but in this case it only contains a value (the array with no key).
If you take out the curly braces, it should work properly. Did you include them because you saw it done elsewhere? If so, you should use parentheses (`()`) instead of curly braces.
Remember that using `eval` on JSON strings can pose security risks. It's better to use a JSON parser that doesn't rely on `eval` (like json2.js, which uses `eval` cautiously after ensuring safety measures are in place), for maximum security. While parentheses help, they are not a foolproof solution.
Check out this tip!
var jsonData = "{key1:'value1',key2:'value2',arrayKey:['content1','content2']}";
var object = eval('(' + jsonData + ')');
var objectCount=0;
for(_object in object) objectCount++;
alert(objectCount);
Give this a try:
var people = {
"person1" : {
"Name": "Alice",
"Address": "Canada"
},
"person2" : {
"Name": "Bob",
"Address": "UK"
}
};
Object.prototype.count = function() {
var self = this,
count = 0;
for(prop in self) {
if(self.hasOwnProperty(prop)) {
count++;
}
}
return count;
};
alert(people.count());
This method can handle nested objects like:
var people = {
"person1" : {
"Name": "Alice",
"Address": "Canada"
},
"person2" : {
"Name": "Bob",
"Address": "UK" ,
"users": {
"person1" : {
"Name": "Alice",
"Address": "Canada"
},
"person2" : {
"Name": "Bob",
"Address": "UK"
}
}
}
};
alert(people.person2.users.count());
edit — Now, with advancements in technology, APIs like Object.keys(), Object.getOwnPropertyNames(), and Object.getOwnPropertySymbols can be utilized to determine the number of properties in an object:
var props = Object.getOwnPropertySymbols(someObject);
var length = props.length; // Total number of properties
Based on my personal experience, the necessity to know the exact count of properties in an object has been rare. Typically, when dealing with unfamiliar objects, focus lies on specific properties (by name). Nonetheless, using these APIs is totally acceptable.
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