Jquery every - 停止循环并返回对象

Question

谁能告诉我为什么循环在 5 条目之后没有停止？

http://jsbin.com/ucuqot/edit#preview

---

$(document).ready(function()
{
  someArray = new Array();
  someArray[0] = 't5';
  someArray[1] = 'z12';
  someArray[2] = 'b88';
  someArray[3] = 's55';
  someArray[4] = 'e51';
  someArray[5] = 'o322';
  someArray[6] = 'i22';
  someArray[7] = 'k954';  

  var test =  findXX('o322');   

});

function findXX(word)
{  
  $.each(someArray, function(i)
  {
    $('body').append('-> '+i+'<br />');
    if(someArray[i] == 'someArray')
    {
      return someArray[i]; //<--- did not stop the loop!
    }   
  });  
}

Answer 1

因为当您在 each 循环中使用 return 语句时，“非 false”值将充当 continue，而 false 将充当中断。您需要从 each 函数返回 false。像这样的东西：

function findXX(word) {
    var toReturn; 
    $.each(someArray, function(i) {
        $('body').append('-> '+i+'<br />');
        if(someArray[i] == word) {
            toReturn = someArray[i];
            return false;
        }   
    }); 
    return toReturn; 
}

来自 docs：

我们可以通过使
回调函数返回 false。返回非 false 与 a 相同
for 循环中的 continue 语句；它会立即跳到下一个
迭代。

Answer 2

修改后的 $.each 函数

$.fn.eachReturn = function(arr, callback) {
   var result = null;
   $.each(arr, function(index, value){
       var test = callback(index, value);
       if (test) {
           result = test;
           return false;
       }
   });
   return result ;
}

它将在非假/非空结果上中断循环并将其返回，所以在你的情况下它将是

return $.eachReturn(someArray, function(i){
    ...

Answer 3

这里：

http://jsbin.com/ucuqot/3/edit

function findXX(word)
{  
  $.each(someArray, function(i,n)
  {
    $('body').append('-> '+i+'<br />');
    if(n == word)
    {
      return false;
    }   
  });  
}

Answer 4

试试这个...

  someArray = new Array();
  someArray[0] = 't5';
  someArray[1] = 'z12';
  someArray[2] = 'b88';
  someArray[3] = 's55';
  someArray[4] = 'e51';
  someArray[5] = 'o322';
  someArray[6] = 'i22';
  someArray[7] = 'k954';  

  var test =  findXX('o322'); 
  console.log(test);



function findXX(word)
{  
  for(var i in someArray){


    if(someArray[i] == word)
    {
      return someArray[i]; //<---  stop the loop!
    }   
  }
}

Answer 5

“我们可以通过以下方式在特定迭代中打破 $.each() 循环
回调函数返回 false。返回非 false 与
for 循环中的 continue 语句；它会立即跳到
下一次迭代。”

来自 http://api.jquery.com/jquery.each/

是的，这很旧，但是，只是为了回答这个问题，这可以更简单一些：

function findXX(word) {
  $.each(someArray, function(index, value) {
    $('body').append('-> ' + index + ":" + value + '<br />');
    return !(value == word);
  });
}
$(function() {
  someArray = new Array();
  someArray[0] = 't5';
  someArray[1] = 'z12';
  someArray[2] = 'b88';
  someArray[3] = 's55';
  someArray[4] = 'e51';
  someArray[5] = 'o322';
  someArray[6] = 'i22';
  someArray[7] = 'k954';
  findXX('o322');
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>

多一点评论：

function findXX(myA, word) {
  let br = '<br />';//create once
  let myHolder = $("<div />");//get a holder to not hit DOM a lot
  let found = false;//default return
  $.each(myA, function(index, value) {
    found = (value == word);
    myHolder.append('-> ' + index + ":" + value + br);
    return !found;
  });
  $('body').append(myHolder.html());// hit DOM once
  return found;
}
$(function() {
  // no horrid global array, easier array setup;
  let someArray = ['t5', 'z12', 'b88', 's55', 'e51', 'o322', 'i22', 'k954'];
  // pass the array and the value we want to find, return back a value
  let test = findXX(someArray, 'o322');
  $('body').append("<div>Found:" + test + "</div>");
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>

注意：数组 .includes() 可能更适合这里 https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/includes

或者只是.find() 获取 https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/find

Answer 6

使用 JavaScript 的 Array.prototype.find 来查找数组中的匹配项可能比设置标志更优雅。一旦回调返回真值，循环就会结束，迭代期间的数组值将是 .find 调用的返回值：

function findXX(word) {
    return someArray.find((item, i) => {
        $('body').append('-> '+i+'<br />');
        return item === word;
    }); 
}

const someArray = new Array();
someArray[0] = 't5';
someArray[1] = 'z12';
someArray[2] = 'b88';
someArray[3] = 's55';
someArray[4] = 'e51';
someArray[5] = 'o322';
someArray[6] = 'i22';
someArray[7] = 'k954';

var test = findXX('o322');
console.log('found word:', test);

function findXX(word) {
  return someArray.find((item, i) => {
    $('body').append('-> ' + i + '<br />');
    return item === word;
  });
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>