I am trying to extract the names of all keys from an array of objects keeping time complexity as n(One loop only). The array is as below:
var addressArray = [{"city":"New York"},{"country":"USA"},{"zip": 45677}];
I want to extract the below:
var addressKeys = ["city", "country", "zip"].
I am able to do the same by first looping through the array and then using a key in obj loop but that doesn't loo good. Alternatives are most welcome.
Use Object.keys to get the keys.
if (typeof Object.keys !== "function") {
(function() {
Object.keys = Object_keys;
function Object_keys(objectToGet) {
var keys = [], name;
for (name in objectToGet) {
if (objectToGet.hasOwnProperty(name)) {
keys.push(name);
}
}
return keys;
}
})();
}
From your definition addressArray is an object not an array.
You can use Object.keys() to get the keys array of an object.
var addressKeys = Object.keys(addressArray);
To support older browsers, which does not support Object.keys you can use a Polyfill
Object and do some OOP methods. Test at : jsperf.com/object-keys-vs-for-inUse for-in loop to access each key-value pair and then push to new array: (Recommended)
for(var index in addressArray){
addressKeys.push(index)
}
Another solution is:
var addressKeys = Object.keys(addressArray)
which is slower comparatively.
Note that I switched []'s with {}'s:
var addressObject = {"city":"New York", "country":"USA", "zip": 45677};
var keys = [];
for(var address in addressObject)
{
keys.push(address);
}
console.log(keys);
addressArrayis not an array, it is an object