javascriptif-statementkhan-academy

Khan Academy: If Statements 2


My if statement is not working, like last time but this time the line won't x = x - 2; in my if statement (I didn't do the else if because I thought it's the problem). Link: https://www.khanacademy.org/computer-programming/probability/5609184564559872. Code:

var x = 78;
var y = 18;

// Just in case I test
var saveX = 78;
var saveY = 18;

draw = function() {
    background(150, 255, 250);
    
    strokeWeight(1);
    stroke(0, 0, 0);
    rect(78, 20, 254, 25);
    
    strokeWeight(6);
    stroke(255, 0, 0);
    line(x, y, x, y + 29);
    
    
    if (x > 332) {
        x = x - 2;
    }
    
    if (x < 78) {
        x = x + 2;
    }
    
    x = x + 2;
};


Solution

  • it works, and the x = x+2 makes the value is not changing at all

    This is what you want for a ping-pong effect, key is the direction variable.

    var x = 78;
    var y = 18;
    
    // Just in case I test
    var saveX = 78;
    var saveY = 18;
    var direction = 1;
    
    draw = function() {
        background(150, 255, 250);
        
        strokeWeight(1);
        stroke(0, 0, 0);
        rect(78, 20, 254, 25);
        
        strokeWeight(6);
        stroke(255, 0, 0);
        line(x, y, x, y + 29);
        
        
        if (x > 332) {
            direction = -1;
        }
        
        if (x < 78) {
            direction = 1;
        }
        
        x = x + direction * 2;
    };