返回值在foreach里面 [英] return value inside foreach

问题描述

  let cookieValue ='';这是一个非常奇怪的事情，我有一个像这样的foreach函数： 
 
 cookieList.forEach（function（cookieItem）{
 const cookieParts = cookieItem.split（'='）; 
 const value = cookieParts [1]; 
 const key = cookieParts [0]; 
 if（key.trim（）=== cookieName）{
 cookieValue = value; 
 return cookieValue; 
} 
}） ; 
 
返回cookieValue; 
  

可以正常工作，但是当我将if语句中的行更改为单行时： p>

 返回值; 
  

它始终返回undefined

有什么想法可以在这里发生？

解决方案

返回的forEach被忽略，但你可以使用映射和过滤器：

  function getCookieValue（cookieList，cookieName）{
 var val = cookieList.map（function（cookieItem）{
 var cookieParts = cookieItem.split（'='）; 
 var value = cookieParts [1]; 
 var key = cookieParts [0]; 
 return（key.trim（）=== cookieName ）？value：null; 
}）
 .filter（（value）=> {return value！= null}）[0]; 
返回val; 
 
 
 let cookieValue = getCookieValue（[key1 = val1，key2 = val2]，key2）; //> val2
  

So this is very weird, I have a foreach function like this:

  let cookieValue = '';

  cookieList.forEach(function(cookieItem) {
    const cookieParts = cookieItem.split('=');
    const value = cookieParts[1];
    const key = cookieParts[0];
    if (key.trim() === cookieName) {
      cookieValue = value;
      return cookieValue;
    }
  });

  return cookieValue;

which works fine, however when I change the lines inside the if statement to a single line:

return value;

It returns undefined always.

Any ideas of what can be happening here?

解决方案

The return of forEach is ignored but you can use map and filter:

function getCookieValue(cookieList, cookieName) {
    var val = cookieList.map(function(cookieItem) {
        var cookieParts = cookieItem.split('=');
        var value = cookieParts[1];
        var key = cookieParts[0];
        return (key.trim() === cookieName) ? value : null;
    })
    .filter((value) => { return value != null })[0];
    return val;
}

let cookieValue = getCookieValue(["key1=val1", "key2=val2"], "key2"); // > "val2"

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