如何使if语句只为真一次？ [英] How to make if statement true only once?

问题描述

如何使if语句只运行一次。我正在用javascript制作一个游戏，一旦用户得分为5，我想在阵列中添加一个新的敌人。我遇到的问题是，如果if语句为真，它会不断添加新的敌人，直到整个屏幕被敌人覆盖。我希望它在得分为5时只添加1个新敌人，然后在得分为10时添加另一个敌人等等。我无法想到实现这一目标的方法。谢谢。

How do I make an if statement run only once. I am making a game in javascript and once the users score is 5 I want to add a new enemy into the array. The problem I am having is once the if statement is true it keeps adding new enemies over and over until the whole screen is covered with enemies. I want it to add only 1 new enemy when score is 5 then another when score is 10 and so on. I cannot think of a way to accomplish this. Thank You.

Sketch.js

Sketch.js

   var score = 0;

   //3 three enemies once game starts
   function StartingEnemies() { 
      for (var i = 0; i < 2; i++) {
        enemies[i] = new BasicEnemy();
      }
   }


   //add new enemies into the array
   function spawnNewEnemies() {
     enemies.push(new BasicEnemy());
   }


   if (score == 5) {
     spawnNewEnemies();
   }

推荐答案

var addNew=true;
if (score == 5 && addNew) {
  spawnNewEnemies();
  addNew=false;
}

如果您正在运行函数内部的代码，请确保addNew是在某个地方声明它会在通话之间保持不变。

If you are running the code inside of a function, make sure that addNew is declared somewhere that it will persist between calls.

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