Underscore.js _.compose() Function

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The _.compose() function is used to return the composition of the list of functions. The list of the function returns the value of the function that follows.

Syntax:

_.compose(*functions)

Parameters: This function accept a single parameter as mentioned above and described below:

functions: It contains the list of function that to be executed.

Return Value: It returns the composition of list of functions.

Below examples illustrate the _.compose() function in Underscore.js:

Example 1:

<!DOCTYPE html> 
<html> 
  
<head> 
    <script type="text/javascript" src= 
"https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.9.1/underscore-min.js"> 
    </script> 
</head> 
  
<body> 
    <script type="text/javascript"> 
        var fun1 = function (addString) { 
            return "Welcome to " + addString; 
        }; 
  
        var fun2 = function (GFG) { 
            return GFG; 
        }; 
        var str = _.compose(fun1, fun2); 
  
        console.log(str('zambiatek')); 
    </script> 
</body> 
  
</html> 

Output:

Example 2:

<!DOCTYPE html> 
<html> 
  
<head> 
    <script type="text/javascript" src= 
"https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.9.1/underscore-min.js"> 
    </script> 
</head> 
  
<body> 
    <script type="text/javascript"> 
        var fun1 = function (str1) { 
            return 'Welcome' + str1 + 
                '\nA computer science portal'; 
        }; 
  
        var fun2 = function (str2) { 
            return ' to ' + str2.toLowerCase(); 
        }; 
        var str = _.compose(fun1, fun2); 
  
        console.log(str('GEEKSFORGEEKS')); 
    </script> 
</body> 
  
</html> 