The syntax of the keys() method is:
Object.keys(obj)
The keys() method, being a static method, is called using the Object class name.
keys() Parameters
The keys() method takes in:
- obj - The object whose enumerable properties are to be returned.
Return value from keys()
- Returns an array of strings that represent all the enumerable properties of the given object.
Note: The ordering of the properties is the same as that when looping over them manually.
Example: Using Object.keys()
// Array objects
const arr = ["A", "B", "C"];
console.log(Object.keys(arr)); // ['0', '1', '2']
// array-like objects
const obj = { 65: "A", 66: "B", 67: "C" };
console.log(Object.keys(obj)); // ['65', '66', '67']
// random key ordering
const obj1 = { 42: "a", 22: "b", 71: "c" };
console.log(Object.keys(obj1)); // ['22', '42', '71']
// string => from ES2015+, non objects are coerced to object
const string = "code";
console.log(Object.keys(string)); // [ '0', '1', '2', '3' ]
Output
[ '0', '1', '2' ] [ '65', '66', '67' ] [ '22', '42', '71' ] [ '0', '1', '2', '3' ]
Recommended Reading: Javascript Object entries()