strategy pattern

var Actor = function(name) {
    this.bagWeight = 20;
    this.name = name;
    this.velocity = 100;
    this.command = "";
};
 
Actor.prototype = {
    setCommand: function(command) {
        this.command = command;
        return this;
    },
 
    play: function() {
        this.command.exec(this);
    }
};
 
let walk = {
    exec: function(actor) {
        showText(actor.name + ' walk velocity : ' + String(actor.velocity));
    }
};
 
let Run = function() {
    this.calc = function(actor) {
        return actor.velocity - actor.bagWeight/2;
    }
   
    this.exec = function(actor) {
        showText(actor.name + ' run velocity : ' + String(this.calc(actor)));
    }
};
 
let Swim = function() {
    this.disadvantage = 30;
    this.calc = function(actor) {
        return actor.velocity - (actor.bagWeight + this.disadvantage);
    }
   
    this.exec = function(actor) {
        showText(actor.name + ' swim velocity : ' + String(this.calc(actor)));
    }
};
 
function run() {
    let actor = new Actor('kim');
   
    let actor1 = new Actor('lee');
    actor1.velocity = 120;   
   
    actor.setCommand(walk).play();
    actor.setCommand(new Run).play();   
    actor.setCommand(new Swim).play();
   
    actor1.setCommand(new Swim).play();
}

run();

function showText(str) {
    document.body.innerHTML += `<p>${str}</p>`;
}