Can I define custom operator overloads in Javascript? [duplicate]

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青春惊慌失措

2020-11-30 07:06

I agree that the equal function on the vector prototype is the best solution. Note that you can also build other infix-like operators via chaining.

function Vector(x, y, z) {
    this.x = x;
    this.y = y;
    this.z = z;
}

Vector.prototype.add = function (v2) {
    var v = new Vector(this.x + v2.x,
                       this.y + v2.y,
                       this.z + v2.z);
    return v;
}

Vector.prototype.equal = function (v2) {
    return this.x == v2.x && this.y == v2.y && this.z == v2.z;
}

You can see online sample here.

Update: Here's a more extensive sample of creating a Factory function that supports chaining.

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自闭症患者

2020-11-30 07:08

No, it's not part of the spec (which doesn't mean that there aren't some hacks).

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醉梦人生

2020-11-30 07:16
No, JavaScript doesn’t support operator overloading. You will need to write a method that does this:
```
Vector.prototype.equalTo = function(other) {
    if (!(other instanceof Vector)) return false;
    return a.x == b.x && a.y == b.y && a.z == b.z;
}
```
Then you can use that method like:
```
vect1.equalTo(vect2)
```
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忘了有多久

2020-11-30 07:16

It isn't a direct answer for you question but it's worth to note.

PaperScript is a simple extension of JavaScript that adds support for operator overloading to any object.

It used for for making Vector graphics on top of HTML5 Canvas.

It parse PaperScript to JavaScript on script tag with type="text/paperscript":

<!DOCTYPE html>
<html>
<head>
<!-- Load the Paper.js library -->
<script type="text/javascript" src="js/paper.js"></script>
<!-- Define inlined PaperScript associate it with myCanvas -->
<script type="text/paperscript" canvas="myCanvas">
  // Define a point to start with
  var point1 = new Point(10, 20);

  // Create a second point that is 4 times the first one.
  // This is the same as creating a new point with x and y
  // of point1 multiplied by 4:
  var point2 = point1 * 4;
  console.log(point2); // { x: 40, y: 80 }

  // Now we calculate the difference between the two.
  var point3 = point2 - point1;
  console.log(point3); // { x: 30, y: 60 }

  // Create yet another point, with a numeric value added to point3:
  var point4 = point3 + 30;
  console.log(point4); // { x: 60, y: 90 }

  // How about a third of that?
  var point5 = point4 / 3;
  console.log(point5); // { x: 20, y: 30 }

  // Multiplying two points with each other multiplies each 
  // coordinate seperately
  var point6 = point5 * new Point(3, 2);
  console.log(point6); // { x: 60, y: 60 }

  var point7 = new Point(10, 20);
  var point8 = point7 + { x: 100, y: 100 };
  console.log(point8); // { x: 110, y: 120 }

  // Adding size objects to points work too,
  // forcing them to be converted to a point first
  var point9 = point8 + new Size(50, 100);
  console.log(point9); // { x: 160, y: 220 }

  // And using the object notation for size works just as well:
  var point10 = point9 + { width: 40, height: 80 };
  console.log(point10); // { x: 200, y: 300 }

  // How about adding a point in array notation instead?
  var point5 = point10 + [100, 0];
  console.log(point5); // { x: 300, y: 300 }
</script>
</head>
<body>
  <canvas id="myCanvas" resize></canvas>
</body>
</html>

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遇见更好的自我

2020-11-30 07:21

The best you can do if you want to stick with the == operator:

function Vector(x, y, z) {
  this.x = x;
  this.y = y;
  this.z = z;
}

Vector.prototype.toString = function () {
  return this.x + ";" + this.y + ";" + this.z;
};

var a = new Vector(1, 2, 3);
var b = new Vector(1, 2, 3);
var c = new Vector(4, 5, 6);


alert( String(a) == b ); // true
alert( String(a) == c ); // false
alert( a == b + "" );    // true again (no object wrapper but a bit more ugly)

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感情败类

2020-11-30 07:24
You can change built-in methods of objects in JavaScript, such as valueOf() method. For any two objects to apply the following operators >, <, <=, >=, -, + JavaScript takes the property valueOf() of each object, so it deals with operators kind of like this: obj1.valueOf() == obj2.valueOf() (this does behind the scenes). You can overwrite the valueOf() method depends on your needs. So for example:
```
var Person = function(age, name){
    this.age = age;
    this.name = name;
} 

Person.prototype.valueOf(){
    return this.age;
}

var p1 = new Person(20, "Bob"), 
    p2 = new Person(30, "Bony");

console.log(p1 > p2); //false
console.log(p1 < p2); //true
console.log(p2 - p1); //10
console.log(p2 + p1); //40

//for == you should the following
console.log(p2 >= p1 && p2 <= p1); // false
```
So this is not the precise answer for your question, but I think this can be an useful stuff for that kind of issues.
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