Extract parameter

Last modified: 08 October 2024

Refactor | Extract/Introduce | Parameter

The Extract Parameter refactoring is used to add a new parameter to a function declaration and to update the function calls accordingly.

https://resources.jetbrains.com/help/img/idea/2025.1/ps_extract_parameter.png
Gif

note

By default, this extract refactoring will be applied in the editor via in-line controls. To change your settings to apply the refactoring via a modal, open the Settings dialog () , go to Editor | Code Editing, and in the Refactorings area select In modal dialogs.

PHP Example

In the example below, a new parameter $c is added to the Calculate() function to replace 10:

Before

After

class Class1 {
    public function Calculate($i){
        while ( $i < 10 ) {
            $i = $i + 1;
        };
        return $i;
    }

    public function DisplaySum(){
        $a = 1;
        $result = $this -> Calculate($a);
        echo "The final result is " . $result;
    }
}
class Class1 {
    public function Calculate($i,$c){
        while ( $i < $c ) {
            $i = $i + 1;
        };
        return $i;
    }

    public function DisplaySum(){
        $a = 1;
        $result = $this -> Calculate($a, 10);
        echo "The final result is " . $result;
    }
}

JavaScript Example

Before

After

A new parameter will be added to this function to replace the 1's: 

function calculate_sum(i) {
    alert('Adding ' + 1 + ' to ' + i);
    return (1 + i);
}

function show_sum() {
    alert('Result: ' + calculate_sum(5));
    }

The new parameter i2 has been added as an optional parameter: 

function calculate_sum(i, i2) {
    i2 = i2 || 1;
    alert('Adding ' + i2 + ' to ' + i);
    return (i2 + i);
}

function show_sum() {
// The function call has not changed:
    alert('Result: ' + calculate_sum(5));
}

A new parameter will be added to this function to replace the 1's. When adding a new parameter we'll specify that it should be a required one. 

function calculate_sum(i) {
    alert('Adding ' + 1 + ' to ' + i);
    return (1 + i);
}

function show_sum() {
    alert('Result: ' + calculate_sum(5));
}

The new parameter i2 has been added as a required parameter: 

function calculate_sum(i, i2) {
    alert('Adding ' + i2 + ' to ' + i);
    return (i2 + i);
}

function show_sum() {
    alert('Result: ' + calculate_sum(5, 1));
}

For more information, refer to Extract Parameter in JavaScript.

See also

Procedures