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p5.js | keyPressed() Function

  • Last Updated : 27 Mar, 2020

The keyPressed() function is invoked whenever a key is pressed. The most recently typed ASCII key is stored into the ‘key’ variable, however it does not distinguish between uppercase and lowercase characters. The non-ASCII character codes can be accessed in the ‘keyCode’ variable with their respective names.

Holding down a key may cause multiple keyPressed() calls. This is due to how the Operating System handles keypresses and depends on how the computer is configured. A browser may have its own default behavior attached to various keys. This can be prevented by adding “return false” to the end of the method.

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Syntax:

keyPressed()

Parameters: This method does not accept any parameters.



Below examples illustrate the keyPressed() function in p5.js:

Example 1:




function setup() {
  createCanvas(600, 200);
  textSize(20);
  text("Press any key to display it "
          + "on the screen", 10, 20);
}
  
function keyPressed() {
  clear();
  textSize(20);
  text("Press any key to display it "
          + "on the screen", 10, 20);
  textSize(100);
  text(key, 100, 150);
}

Output:
display-pressed

Example 2:




let opac = 128;
  
function setup() {
  createCanvas(700, 200);
  background(0, 128, 0, opac);
  textSize(22);
  text("Press the left and right arrow"
        + " keys to change the opacity"
        + " of the color.", 10, 20);
}
  
function keyPressed() {
  clear();
  
  textSize(50);
  text("Pressing: " + key, 100, 150);
  
  // Reduce opacity if the left arrow is pressed
  if (key == "ArrowLeft" && opac > 0)
    opac -= 20;
  // Increase opacity if the left arrow is pressed
  else if (key == "ArrowRight" && opac < 255)
    opac += 20;
  
  // Set the new background color
  background(0, 128, 0, opac);
  
  textSize(22);
  text("Press the left and right arrow"
        + " keys to change the opacity"
        + " of the color.", 10, 20);
}

Output:
change-opacity

Online editor: https://editor.p5js.org/

Environment Setup: https://www.geeksforgeeks.org/p5-js-soundfile-object-installation-and-methods/

Reference: https://p5js.org/reference/#/p5/keyPressed




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