How to use the hasOwnProperty method In Typescript
The ‘hasOwnProperty’ method is a TypeScript built-in method that we use to check if an object has a property with a specific key. It returns a boolean value and is used when we want to explicitly check for the existence of a property.
Syntax
if(dictionary.hasOwnProperty(key)){
// key exists
} else{
// key does not exist
}
Example: The below code uses the ‘hasOwnProperty’ method to check if a key exists in dictionary in TypeScript.
interface Dictionary{
[key:string]:string;
}
let dictionary:Dictionary = {
"name": "w3wiki",
"desc": "A computer science portal",
"est": "2009" };
let keyToCheck:string = "name";
if (dictionary.hasOwnProperty(keyToCheck)) {
console.log(
`Key ${keyToCheck} exists in the dictionary.`);
} else {
console.log(
`Key ${keyToCheck} doesn't exist in the dictionary.`);
}
Output:
"Key name exists in the dictionary."
How to Check if a Key Exists in a Dictionary in TypeScript ?
In TypeScript dictionaries are used whenever the data is needed to be stored in key and value form. We often retrieve the data from the dictionaries using an associated key. Therefore it becomes crucial to check whether the key exists in a dictionary or not.
We can use the below methods to check if a key exists or not in a dictionary.
Table of Content
- Using an ‘in’ operator
- Using the hasOwnProperty method
- Using the undefined keyword
- Using the Map object
- Using for loop