JavaScript: in Operator

Last update on May 28 2022 10:33:38 (UTC/GMT +8 hours)

Description

The in operator is used to check whether a given property is available on an object.

Syntax

property in object

Parameters

property: Name of the property.

object: Name of the object.

Example:

The following web document shows how the in operator is used.

HTML Code

<!doctype html><head>
<meta charset="utf-8">
<title>JavaScript in operator example</title>
<meta name="description" content="This document contains an example of JavaScript in operator" />
</head>
<script src="javascript-in-operator-example1.js"></script>
</body>
</html>

JS Code

var employeeobj = {name:"Robert",designation:"Officer",age:"34"};
if ("designation" in employeeobj)
{
console.log('Designation property is present'); 
}
else
{
console.log('Designation property is not present'); 
}

View the example in the browser

Practice the example online

See the Pen in-1 by w3resource (@w3resource) on CodePen.

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JavaScript: Tips of the Day

How to insert an item into an array at a specific index (JavaScript)?

What you want is the splice function on the native array object.

arr.splice(index, 0, item); will insert item into arr at the specified index (deleting 0 items first, that is, it's just an insert). In this example we will create an array and add an element to it into index 2:

var arr = [];
arr[0] = "Jani";
arr[1] = "Hege";
arr[2] = "Stale";
arr[3] = "Kai Jim";
arr[4] = "Borge";

console.log(arr.join());
arr.splice(2, 0, "Lene");
console.log(arr.join());

Ref: https://bit.ly/2BXbp04