Question

我必须检查对象是否包含javascript中的值，而我不知道该怎么做。该对象如下所示：

Match {
  player1: undefined,
  player2: undefined,
  childrenLeft: 
   Match {
     player1: 'John',
     player2: 'Mary',
     childrenLeft: undefined,
     childrenRight: undefined },
  childrenRight: 
   Match {
     player1: 'Michael',
     player2: 'James',
     childrenLeft: undefined,
     childrenRight: undefined }
  }

现在这是一场有决赛和两场半决赛的比赛，但是根据球员的数量可能要大得多，所以我需要遍历所有的树。我有这个功能，假设返回下一个对手但是当我在childrenLeft上搜索玩家时它不起作用。所以，当我执行Match.nextOpponent（James）时，我得到了迈克尔＆＃39;因此，当我执行Match.nextOpponent（Mary）时，我得到了“未定义的”＃。

Match.prototype.nextOpponent = function (player) {
    if (this.player1 === player) return this.player2;
    if (this.player2 === player) return this.player1;
    if (!this.player2 && !this.player1 && this.childrenRight !== undefined) return this.childrenRight.nextOpponent(player);
    if (!this.player1 && !this.player2 && this.childrenLeft !== undefined) return this.childrenLeft.nextOpponent(player);
}

有人可以帮忙吗？非常感谢你

Answer 1

问题出现的原因是最后两个return块中的if，即使递归调用的返回值为undefined。这意味着如果第一个if条件为真，则无法尝试第二个if条件。

所以要解决这个问题，请使用以下代码：

Match.prototype.nextOpponent = function (player) {
    if (this.player1 === player) return this.player2;
    if (this.player2 === player) return this.player1;
    var match;
    if (!this.player2 && !this.player1 && this.childrenRight) 
        match = this.childrenRight.nextOpponent(player);
    // maybe previous return value was undefined, then try the other side:
    if (!match && !this.player1 && !this.player2 && this.childrenLeft) 
        match = this.childrenLeft.nextOpponent(player);
    return match;
}

＆＃13;

function Match(p1, p2) {
    this.player1 = p1;
    this.player2 = p2;
    this.childrenLeft = undefined;
    this.childrenRight = undefined;
}

Match.prototype.nextOpponent = function (player) {
    if (this.player1 === player) return this.player2;
    if (this.player2 === player) return this.player1;
    var match;
    if (!this.player2 && !this.player1 && this.childrenRight) 
        match = this.childrenRight.nextOpponent(player);
    if (!match && !this.player1 && !this.player2 && this.childrenLeft) 
        match = this.childrenLeft.nextOpponent(player);
    return match;
}

var root = new Match();
root.childrenLeft = new Match('John', 'Mary'); 
root.childrenRight = new Match('Michael', 'James'); 

console.log('James plays: ', root.nextOpponent('James'));
console.log('Mary plays: ', root.nextOpponent('Mary'));

＆＃13;

注意：您不必将childrenLeft与undefined进行比较。由于undefined是假的，任何对象都是真实的，您只需评估childrenLeft条件下的if。

在嵌套对象中搜索值

1 个答案: