Passing a function as a parameter in JavaScript
Passing a function as an argument to the function is quite similar to the passing variable as an argument to the function. so variables can be returned from a function. The below examples describe passing a function as a parameter to another function.
Example 1: This example passes a function geeks_inner to the function geeks_outer as an argument.
html
<!DOCTYPE html> <html> <head> <title> JavaScript | Pass a function as parameter </title> </head> <body style = "text-align:center;"> <h1 style = "color:green;" > GeeksForGeeks </h1> <p> Passing function as arguments. </p> <!-- Function call after clicking the button --> <button onclick = "geeks_outer(geeks_inner)"> Click Here </button> <script> function geeks_inner(value){ return 'hello User!'; } function geeks_outer(func){ alert(func()); } </script> </body> </html> |
Output:
- Before clicking on the button:
- After clicking on the button:
Example 2: This example passes a function geeks_inner along with an argument ‘Geeks!’ to the function geeks_outer as an argument.
html
<!DOCTYPE html> <html> <head> <title> JavaScript | Pass a function as parameter </title> </head> <body style = "text-align:center;"> <h1 style = "color:green;" > GeeksForGeeks </h1> <p> Passing function as arguments. </p> <button onclick = "geeks_outer('Geeks!', geeks_inner)"> Click Here </button> <!-- Script to uses function call using function as argument --> <script> function geeks_inner(value){ return 'hello '+value; } function geeks_outer(a, func){ alert(func(a)); } </script> </body> </html> |
Output:
- Before clicking on the button:
- After clicking on the button:
Example 3: Here in this example, smaller function is passed as an argument in the sayHello function. so here actually we are passing a smaller function address to the function sayHello.
Javascript
function sayHello(param){ console.log("hello",param); param(); return "Hiii Geeks for Geeks" } //function address function smaller(){ console.log("Is everything alright") } //function call const returnHello= sayHello(smaller) console.log(returnHello) |
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