Question

我一直在尝试使用二维数组的for循环，显然我是javascript和编程的新手一般..我试图找到数组内的var如果找到然后输出成功消息，如果没有输出失败的消息。每当我输出代码输出失败的消息时，它会在控制台上显示4次，成功消息仍会显示..

如果失败则预期输出：

No matching keyword was found

结果输出：

The keyword String is found 
No matching keyword was found 
No matching keyword was found 
No matching keyword was found 
No matching keyword was found

newArray = [["String","Sa"],[1,2,35]];


var find = "String";
for(var i=0; i< newArray.length;i++){
    for(var j=0; j < newArray.length + i; j++){
        if (newArray[i][j] === find){
            console.log("The keyword " + find + " is found");
        } else {
            console.log("No matching keyword was found");
        }
    }

}

Answer 1

就像他们所说的那样，使用变量作为指标。

newArray = [["String","Sa"],[1,2,35]];


var find = "String";
var found = false;
for(var i=0; i< newArray.length;i++){
    for(var j=0; j < newArray[i].length + i; j++){
        if (newArray[i][j] === find){
            console.log("The keyword " + find + " is found");
            found = true;
        }
    }

}
if (!found) {
    console.log("No matching keyword was found");
}

请分析并比较我们的代码，以防止您将来提出类似的问题。

现在，在我们＆＃34;发现＆＃34;之后，尝试优化上述内容，而不是迭代其他元素。它的匹配。

Answer 2

你的第二个循环不正确。

在你的内循环中，你必须循环newArray[i] 此外，如果搜索成功，请使用break。

还使用变量来表示操作已结束。

 newArray = [["String","Sa"],[1,2,35]];

 var find = "String";

  var end = false;
   for(var i=0; i< newArray.length;i++){
        for(var j=0; j < newArray[i].length; j++){
               if (newArray[i][j] === find){
                    console.log("The keyword " + find + " is found");
                     end = true;
                     break;
                } else {
                     console.log("No matching keyword was found");
                 }
          }
           if (end) {
                 break;
            }
     }

Answer 3

＆＃13;

newArray = [["String","Sa"],[1,2,35]];


var find = "String";
for(var i=0; i< newArray.length;i++){
    for(var j=0; j < newArray[i].length + i; j++){// <--- you want to iterate only as many times as the inner array elements. Right now you iterate over the same array index as the first loop.
        if (newArray[i][j] === find){
            alert("The keyword " + find + " is found");
            return; //<-- end script after result is found
        } 
    }
}
//Will only get here if the return was not hit
alert("No matching keyword was found");

＆＃13;

你看到它4次，因为循环将继续运行，直到它迭代了所有东西。实现所需目标的一种方法是在找到结果后结束脚本。

如果你想采用光滑的es6方法：

＆＃13;

newArray = [["String","Sa"],[1,2,35,"String"]];
const term = "String2";
const isFound = newArray.some(e=>e.find(e=>e===term));
alert(`The keyword has ${isFound ? "" : "not"} been found`);

＆＃13;

Answer 4

使用布尔值来存储一个标记＆＃34; isFound＆＃34;，并在找到时中断。

newArray = [["String","Sa"],[1,2,35]];
var find = "String";
var isFound = false;
for(var i=0; i< newArray.length;i++){
    for(var j=0; j < newArray.length + i; j++){
        if (newArray[i][j] === find){
            console.log("The keyword " + find + " is found");
            isFound = true;
            break;
        }
    }
}
if (isFound == false){
console.log("No matching keyword was found");
}

Javascript如何才能使'else'输出只有一次？

4 个答案: