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

The extend() function in the Underscore library is used to copy properties of one or more source objects to a destination object. Here's an example of how to use it:

index.tsx
// load underscore library
var _ = require('underscore');

// define destination object
var destinationObj = {name: 'John', age: 30};

// define source objects
var sourceObj1 = {city: 'New York'};
var sourceObj2 = {gender: 'Male'};

// copy properties of source objects to destination object
_.extend(destinationObj, sourceObj1, sourceObj2);

// print the modified destination object
console.log(destinationObj);
413 chars
16 lines

Output:

index.tsx
{
  name: 'John',
  age: 30,
  city: 'New York',
  gender: 'Male'
}
68 chars
7 lines

In the above example, we first load the Underscore library and define a destination object destinationObj. We then define two source objects sourceObj1 and sourceObj2 that contain properties that we want to copy to the destination object. Finally, we call the _.extend() function to copy the properties of the source objects to the destination object. The modified destinationObj is printed to the console.

Note that the _.extend() function modifies the destination object in place and returns it. If two or more source objects contain properties with the same name, the value of the last property in the arguments list will overwrite the previous values.