在 JavaScript 中使用数组的 While 循环

Question

我需要有关 Js 中此代码的帮助。这个例子：

let friends = ["Ahmed", "Sayed", "Ali", 1, 2, "Mahmoud", "Amany"];
let index = 0;
let counter = 0;



// // Output
// "1 => Sayed"
// "2 => Mahmoud"



while(index < friends.length){
    index++;
    if ( typeof friends[index] === "number"){
        continue;
    }
    if (friends[index][counter] === "A"){
        continue;
    }
    console.log(friends[index]);

}

当我这样做时，按摩出现在我面前，

seventh_lesson.js:203 Uncaught TypeError: Cannot read properties of undefined (reading '0') at Seventh_lesson.js:203.

然后我改变了这一行

if (friends[index][counter] === "A"){continue;
}

有了这个

if (friends[index].startsWith("A")){continue;} 

还是不行，不知道为什么？

是数组中有数字的原因吗？

Answer 1

你应该在循环结束时增加index，否则你会跳过第一个元素并超过最后一个元素。

while(index < friends.length){
    if ( typeof friends[index] === "number"){
        continue;
    }
    if (friends[index][counter] === "A"){
        continue;
    }
    console.log(friends[index]);
    index++;
}

遍历数组的更好方法是使用for...of 循环，因此您根本不必使用index。

for(const friend of friends)
    if ( typeof friend === "number"){
        continue;
    }
    if (friend[counter] === "A"){
        continue;
    }
    console.log(friend);
}

Answer 2

试试这个代码

    let friends = ["Ahmed", "Sayed", "Ali", 1, 2, "Mahmoud", "Amany"];
    let index = -1; // Here define index position is -1 because in the while loop first increase index
    
    
    
    // // Output
    // "1 => Sayed"
    // "2 => Mahmoud"
    
    while(index < friends.length-1){
        index++;
         
        if ( typeof friends[index] === "number"){
            continue;
        }
        if (friends[index].charAt(0) === "A"){ // Here used charAt(0) is meance it will check only first letter is A or not If find a then it will continue 
            continue;
        }
       
        console.log(friends[index]);
    
    }

OR 

let friends = ["Ahmed", "Sayed", "Ali", 1, 2, "Mahmoud", "Amany"];
friends.filter((o)=>{
  if(typeof(o)!="number"&&!o.startsWith("A"))
  console.log(o)
})