Better / Faster way to extract value with a matched property on different depth on a nested object with condition

Question

I have an object with inconsistent nesting structure that I have no control over. I need to extract certain value if it met a certain condition.

currently doing it by iterating over the properties recursively and matching the properties with the condition and pushing the matched values to an empty array like this:

var obj = {"a":0,"b":{"x":1,"y":100},"c":[{"x":1,"y":120},{"x":2,"y":140}]};
var extracts = [];
extractProp(obj);

function extractProp(obj){
    for (var key in obj){
        if (key == "x" && obj[key]=="1"){
            extracts.push(obj["y"]);
        } else {
            extractProp(obj[key]);
        }
    }
}
console.log(extracts); //(2) [100, 120]

which allows me to get the expected result. In my previous question, someone pointed out a better way in modifying parts of json by passing reviver parameter on JSON.parse. It got me thinking that there must be a better way to do this too. Are there any native / built-in function in javascript for this?

IMO your current approach is just fine, the intent of the code is quite clear and there isn't really anything more to trim down. I'd prefer an `Object` method over `for..in`, but `for..in` still works fine here — CertainPerformance, Mar 25 '19 at 05:56
Fast thinking, I think reviver function will not allow back reference, so if for instance you wanted the inverse (`x` based on the value of `y`) then you'd be screwed. Your method doesn't look that bad from here, except that I would add a few if(hasOwnProperty) and if(obj && typeof obj === "object") — Kaiido, Mar 25 '19 at 05:56

score 0 · Answer 1 · answered Mar 25 '19 at 06:49

Not quite much better but faster

Check comparision here http://jsben.ch/7OZfP

let obj = { "a": 0, "b": { "x": 1, "y": 100 }, "c": [{ "x": 1, "y": 120 }, { "x": 2, "y": 140 }] };

var extracts = [];
extractProp(obj);

function extractProp() {
 Object.entries(obj).forEach(([key, val]) => {
  if (typeof val === 'object') {
   if (Array.isArray(val)) {
    val.forEach(gety)
   } else {
    gety(val)
   }
  }
 });
}

function gety({ x, y }) {
 if (x == 1 && y)
  extracts.push(y);
}
console.log(extracts); //(2) [100, 120]

Better / Faster way to extract value with a matched property on different depth on a nested object with condition

1 Answers1