In ECMAScript 2021, you can check if a hash (also known as object or dictionary) includes a certain key using the "in" operator or the "hasOwnProperty" method.
1. Using the "in" operator:
To check if a hash includes a key using the "in" operator, write the code like this example:
const myObj = {a: 1, b: 2, c: 3};
if ('a' in myObj) {
console.log('myObj has the key "a"');
} else {
console.log('myObj does not have the key "a"');
}
// Output: myObj has the key "a"
In the example above, we create a hash called "myObj", which includes three keys ("a", "b", and "c"). We then use the "in" operator to check if "myObj" includes the key "a". If it does, we print a message saying that "myObj" has the key "a". If it doesn't, we print a message saying that "myObj" does not have the key "a".
2. Using the "hasOwnProperty" method:
To check if a hash includes a key using the "hasOwnProperty" method, write the code like this example:
const myObj = {a: 1, b: 2, c: 3};
if (myObj.hasOwnProperty('a')) {
console.log('myObj has the key "a"');
} else {
console.log('myObj does not have the key "a"');
}
// Output: myObj has the key "a"
In the example above, we create a hash called "myObj", which includes three keys ("a", "b", and "c"). We then use the "hasOwnProperty" method to check if "myObj" includes the key "a". If it does, we print a message saying that "myObj" has the key "a". If it doesn't, we print a message saying that "myObj" does not have the key "a".