Last Updated : 12 Jul, 2025
JavaScript in operator is an inbuilt operator which is used to check whether a particular property exists in an object or not. It returns a boolean value true if the specified property is in an object, otherwise, it returns false.
Syntax:prop in objectParameters:
This method returns a boolean value. The value true is returned if the specified property is found in an object, else it returns false.
Example 1: Below is an example of the in-operator.
JavaScript
function gfg() {
// Illustration of in operator
const array = ['geeks', 'for',
'geeks']
// Output of the indexed number
console.log(0 in array);
// Output of the Value
console.log('for' in array);
// output of the Array property
console.log('length' in array);
}
gfg();
Example 2: This example shows the use of the in operator in Javascript.
JavaScript
// Illustration of in operator
const array = ['geeksforgeeks', 'geeksfor',
'geeks', 'geeks1']
// Output of the indexed number
console.log(0 in array)
console.log(2 in array)
console.log(5 in array)
// Output of the Value
console.log('for' in array)
console.log('geeksforgeeks' in array)
// output of the Array property
console.log('length' in array)
true true false false false true
Example 3: This example shows the use of the in operator in Javascript.
JavaScript
// Illustration of in operator
const object = {
val1: 'Geeksforgeeks',
val2: 'Javascript',
val3: 'operator',
val4: 'in'
};
console.log('val1' in object);
delete object.val1;
console.log('val1' in object);
if ('val1' in object === false) {
object.val1 = 'GEEKSFORGEEKS';
}
console.log(object.val1);
true false GEEKSFORGEEKSSupported Browsers:
We have a complete list of Javascript Operators, to check those please go through the Javascript Operators Complete Reference article.
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