函数不返回值，仅返回console.logs

Question

I'm new in JS but now I'm totally confused. Why my function print logs into console but I can not return its value?

function searchObj (obj, query) {
    var variableToReturn="";
    for (var key in obj) {
        var value = obj[key];

        if (typeof value === 'object') {
            searchObj(value, query);
        }

        if (value === query) {
            console.log('property=' + key + ' name=' + obj["name"]);
            variableToReturn = obj["name"];
        }
    }
    return variableToReturn;
  }

but if I try that one in my code... it doesn't work at all

var newAttributes =searchObj(position, "1277,1795");

the variable is empty ;( I'm trying to understand it the whole day

I get right values only in my console:

property=backward name=brumi

This is one of the object which I'm looking for:

var position =  {
  current: {
    coordinates: '2408,1822',
    name: 'start',
    premiumPoints: 0,
    points: 0,
    right: Projects.detectProjectByKeyword("moneymat").coordinates,
    left: Projects.detectProjectByKeyword("wohnung").coordinates,
    forward: Projects.detectProjectByKeyword("supermarkt").coordinates,
    backward: "0,0"
  },
  start: //more objects to check

Answer 1

• Modified the code as it seemed it was not working for more than two objects Here is working code:

 var position = { current: { coordinates: '2408,1822', name: 'start', premiumPoints: 0, points: 0, backward: "0,0" }, some: { coordinates: '2409,1822', name: 'Some Start', premiumPoints: 0, points: 0, backward: "0,0" }, more: { coordinates: '2400,1822', name: 'more Start', premiumPoints: 0, points: 0, backward: "0,0" } }; function searchObj(obj, query) { var data =''; for (var property in obj) { if (obj.hasOwnProperty(property)) { if (typeof obj[property] === "object") { data = searchObj(obj[property], query); if(data !='') return data; } else { if (obj[property] === query) { return obj["name"]; } } } } return data; } var data = searchObj(position, "2400,1822") console.log("Result : " +data) 

Since you are using recursive functions inside your code, you need to add "return" in front of them

In above code I have added return in for recursive searchObj(value, query); and obj["name"]; .

let us know if this works

Answer 2

From my understanding what you are trying to do is to recursively search a nested object and check that if there is a value in it that matches the parameter query . The problem with your code is that the variable variableToReturn gets initialised to '' each time the function is called. Since you are not returning variableToReturn when the value matches your query. The function will search through the nested objects until all the keys have been visited. The last key may not contain the value that you desire, and since you declare variableToReturn to "" at the beginning of your code, it will return that value Try running your code in chrome and you will see that you'll the function will return "" . I believe that by adding a return to your recursive call and once you the current value matches the query will solve your issue. So your function should look something like below:

 function searchObj (obj, query) { // loop through the keys in obj for (let key in obj) { let value = obj[key]; if (typeof value === 'object') { // current value is an object, so search recursively return searchObj(value, query); } if (value === query) { // found the value return obj['name']; } } // can't find keys that match, so return empty string return ''; } 

Answer 3

A return statement passes a value back to the immediate caller of the current function's call-frame. In the case of recursion, this immediate caller can be another invocation of that same function.

Hence need to return the result of the recursion, or else the method implicitly returns "undefined"

So,

var position =  {
  current: {
    coordinates: '2408,1822',
    name: 'start',
    premiumPoints: 0,
    points: 0,
    backward: "0,0"
  }
  };

  function searchObj (obj, query) {
    var variableToReturn="";
    for (var key in obj) {
        var value = obj[key];

        if (typeof value === 'object') {
          return  searchObj(value, query);
        }

        if (value === query) {

          variableToReturn = obj["name"];
        }
    }
    return variableToReturn;
  }

  var variableToReturn = searchObj(position, "2408,1822");