如果我有对象的引用:

var test = {};

可能(但不是立即)具有嵌套对象,例如:

{level1: {level2: {level3: "level3"}}};

检查深度嵌套对象中是否存在属性的最佳方法是什么?

警报(测试级别1);生成未定义,但警告(test.level1.level2.level3);失败。

我目前正在做这样的事情:

if(test.level1 && test.level1.level2 && test.level1.level2.level3) {
    alert(test.level1.level2.level3);
}

但我想知道是否有更好的方法。


当前回答

我编写了自己的函数,该函数采用所需的路径,并具有一个好的和坏的回调函数。

function checkForPathInObject(object, path, callbackGood, callbackBad){
    var pathParts = path.split(".");
    var currentObjectPath = object;

    // Test every step to see if it exists in object
    for(var i=0; i<(pathParts.length); i++){
        var currentPathPart = pathParts[i];
        if(!currentObjectPath.hasOwnProperty(pathParts[i])){
            if(callbackBad){
                callbackBad();
            }
            return false;
        } else {
            currentObjectPath = currentObjectPath[pathParts[i]];
        }
    }

    // call full path in callback
    callbackGood();
}

用法:

var testObject = {
    level1:{
        level2:{
            level3:{
            }
        }
    }
};


checkForPathInObject(testObject, "level1.level2.level3", function(){alert("good!")}, function(){alert("bad!")}); // good

checkForPathInObject(testObject, "level1.level2.level3.levelNotThere", function(){alert("good!")}, function(){alert("bad!")}); //bad

其他回答

这是我从奥利弗·斯蒂尔那里学到的一个模式:

var level3 = (((test || {}).level1 || {}).level2 || {}).level3;
alert( level3 );

事实上,整篇文章讨论了如何在javascript中实现这一点。他决定使用上面的语法(一旦你习惯了,它就不那么难读了)作为成语。

getValue (o, key1, key2, key3, key4, key5) {
    try {
      return o[key1][key2][key3][key4][key5]
    } catch (e) {
      return null
    }
}

今天刚刚编写了这个函数,它对嵌套对象中的属性进行了深入搜索,如果找到了,则返回该属性的值。

/**
 * Performs a deep search looking for the existence of a property in a 
 * nested object. Supports namespaced search: Passing a string with
 * a parent sub-object where the property key may exist speeds up
 * search, for instance: Say you have a nested object and you know for 
 * certain the property/literal you're looking for is within a certain
 * sub-object, you can speed the search up by passing "level2Obj.targetProp"
 * @param {object} obj Object to search
 * @param {object} key Key to search for
 * @return {*} Returns the value (if any) located at the key
 */
var getPropByKey = function( obj, key ) {
    var ret = false, ns = key.split("."),
        args = arguments,
        alen = args.length;

    // Search starting with provided namespace
    if ( ns.length > 1 ) {
        obj = (libName).getPropByKey( obj, ns[0] );
        key = ns[1];
    }

    // Look for a property in the object
    if ( key in obj ) {
        return obj[key];
    } else {
        for ( var o in obj ) {
            if ( (libName).isPlainObject( obj[o] ) ) {
                ret = (libName).getPropByKey( obj[o], key );
                if ( ret === 0 || ret === undefined || ret ) {
                    return ret;
                }
            }
        }
    }

    return false;
}

ES6答案,经过彻底测试:)

const propExists = (obj, path) => {
    return !!path.split('.').reduce((obj, prop) => {
        return obj && obj[prop] ? obj[prop] : undefined;
    }, obj)
}

→请参阅具有完整测试覆盖范围的Codepen

我也遇到了同样的问题,我想看看是否能找到自己的解决方案。这接受要检查的路径作为字符串。

function checkPathForTruthy(obj, path) {
  if (/\[[a-zA-Z_]/.test(path)) {
    console.log("Cannot resolve variables in property accessors");
    return false;
  }

  path = path.replace(/\[/g, ".");
  path = path.replace(/]|'|"/g, "");
  path = path.split(".");

  var steps = 0;
  var lastRef = obj;
  var exists = path.every(key => {
    var currentItem = lastRef[path[steps]];
    if (currentItem) {
      lastRef = currentItem;
      steps++;
      return true;
    } else {
      return false;
    }
  });

  return exists;
}

下面是一些日志记录和测试用例的片段:

console.clear();var测试案例=[[“data.Messages[0].Code”,true],[“data.Messages[1].Code”,true],[“data.Messages[0]['Code']”,true],['data.Messages[0][“Code”]',true],[“data[Messages][0]['Code']”,错误],[“data['Messages'][0]['Code']”,真]];var path=“data.Messages[0].Code”;变量obj={数据:{消息:[{代码:“0”}, {代码:“1”}]}}函数checkPathForTruthy(obj,路径){if(/\[[a-zA-Z_]/.test(路径)){console.log(“无法解析属性访问器中的变量”);return false;}path=路径替换(/\[/g,“.”);path=路径替换(/]|'|“/g,”“);path=路径拆分(“.”);var步数=0;var lastRef=obj;var logOutput=[];var exists=path.every(key=>{var currentItem=lastRef[path[steps]];if(currentItem){logOutput.push(currentItem);lastRef=当前项;步骤++;返回true;}其他{return false;}});console.log(存在,logOutput);返回存在;}testCase.forEach(testCase=>{如果(checkPathForTruthy(obj,testCase[0])==testCase[1]){console.log(“通过:”+testCase[0]);}其他{console.log(“失败:”+testCase[0]+“预期”+testCase[1]);}});