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How to find keys of a hash in JavaScript?
In JavaScript, objects act as hash tables where you can store key-value pairs. To extract all keys from an object, use the built-in Object.keys() method, which returns an array of the object's property names.
Syntax
Object.keys(object)
Parameters
object: The object whose keys you want to retrieve.
Return Value
Returns an array of strings representing the object's own enumerable property names (keys).
Example
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Find Hash Keys</title>
<style>
body {
font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
}
.result {
font-size: 18px;
font-weight: 500;
color: green;
margin: 10px 0;
}
.btn {
padding: 10px 20px;
background-color: #007bff;
color: white;
border: none;
border-radius: 4px;
cursor: pointer;
}
</style>
</head>
<body>
<h1>Find Keys of a Hash in JavaScript</h1>
<div class="result"></div>
<button class="btn">DISPLAY KEYS</button>
<h3>Click the button to display the object keys</h3>
<script>
let resEle = document.querySelector(".result");
let obj = {
firstName: "Rohan",
lastName: "Sharma",
age: 22,
city: "Mumbai"
};
document.querySelector(".btn").addEventListener("click", () => {
let keys = Object.keys(obj);
resEle.innerHTML = "Object keys are: " + keys.join(", ");
});
</script>
</body>
</html>
Output
When you click the "DISPLAY KEYS" button, the output will be:
Object keys are: firstName, lastName, age, city
Using Object.keys() in Console
let person = {
name: "Alice",
age: 30,
profession: "Developer"
};
let keys = Object.keys(person);
console.log(keys);
console.log("Number of keys:", keys.length);
['name', 'age', 'profession'] Number of keys: 3
Key Points
-
Object.keys()only returns enumerable own properties, not inherited properties - The order of keys follows the same order as a
for...inloop - It returns an empty array for objects with no enumerable properties
- Works with any object, including arrays (returns array indices as strings)
Conclusion
Object.keys() is the standard method to retrieve all keys from a JavaScript object. It returns an array of strings that you can iterate over or manipulate as needed.
Updated on: 2026-03-15T23:18:59+05:30
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