Question

I’m trying to call a method of all button objects on every mouse click, but I’m not at all familiar with how javascript prototypes work, would greatly appreciate some help. Here’s what I have so far.

var button1 = new button(200, 200, 150, 150, "testFunc();"); 
function button(x,y,width,height, func) {
    this.x = x;
    this.y = y;
    this.width = width;
    this.height = height;
    this.func = func;

}

button.prototype.click = function(clickx, clicky) {
    eval(this.func)
        console.log("Clicked button at" + this.x + " " + clicky);
        if (clickx > this.x && (clickx + width) < this.x) {
            if (clicky > this.y && (clicky + height) < this.y) {

                this.func(); //Call the button's function
            }
        }   
}

function onClick(x, y) {
    button.prototype.click.call(x, y); 
}

I basically want every button object to check if it was clicked using the xy coordinates of the click. Certainly this should be possible with javascript?

Answer 1

Ok, a few things.

1. Constructors should always start with a capital letter. Button not button.
2. Functions are objects, you can pass one right in, without ever using eval for anything.
3. If you want to operate on a list of buttons, you need a list of buttons. Functions in the prototype are shared with all instances, but you can’t get all instances from a prototype. You need to maintain that list yourself. Arrays are good for lists.

---

// Constructor! capitalized!
function Button(x, y, width, height, func) {
    this.x = x;
    this.y = y;
    this.width = width;
    this.height = height;
    this.func = func;
}

// Each constructed Button will have a click() method.
Button.prototype.click = function(clickx, clicky) {
    console.log("Clicked button at" + this.x + " " + clicky);
    if (clickx > this.x && (clickx + width) < this.x) {
        if (clicky > this.y && (clicky + height) < this.y) {
            this.func(); //Call the button's function
        }
    }   
}

// Passed as the function to execute in this not very exciting example.
function testFunc() {
    console.log('called testFunc()!')
}

// Make a bunch of buttons, save them in an array.
// Note how we actually pass a function object as the last argument.
// Note how the last argument IS NOT a string.
var buttons = [
  new Button(100, 100, 150, 150, testFunc),
  new Button(250, 250, 150, 150, testFunc),
  new Button(400, 400, 150, 150, testFunc)
];

// called by something else that passes x and y
function onClick(x, y) {
    // tell each button we had a click, and pass in x and y to see
    // if it should handle it.
    for (var i = 0; i < buttons.length; i++) {
        var button = buttons[i];
        button.click(x, y);
    }
}