how to use the isundefined function from the underscore library in javascript

To use the isUndefined function from the Underscore library in JavaScript, you must first make sure that you have included the library in your code. Once you have done this, you can simply call the isUndefined function and pass in your variable as an argument.

Here is an example code snippet:

index.tsx
// Include the Underscore library
<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.13.1/underscore-min.js"></script>

// Define a variable
var myVariable;

// Check if the variable is undefined using the isUndefined function
if (_.isUndefined(myVariable)) {
    console.log("The variable is undefined");
} else {
    console.log("The variable has a value");
}
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In this example, we first include the Underscore library in our code. We then define a variable called myVariable. We use the isUndefined function from the Underscore library to check if the variable is undefined. If the variable is undefined, we log a message to the console saying that it is undefined. If it has a value, we log a different message to the console.