Accessing Nested Arrays/properties In Javascript

The utility function from this answer allows to easily access nested properties of objects and returns null (or undefined) if one of the parent properties does not exist. original

Solution 1:

The easiest way would be to change the path/key you're passing to get()

From

get(obj, 'key[0].myArray[2]');

To

get(obj, 'key.0.myArray.2');

var get = function(obj, key) {
    return key.split(".").reduce(function(o, x) {
        return (typeof o == "undefined" || o === null) ? o : o[x];
    }, obj);
}

var childArray = [0,1,2]
var parentArray = [{myArray: childArray}]
var obj = {key: parentArray}

console.log(get(obj, 'key.0.myArray.2'));      // 2console.log(get(obj, 'key.0.foo.2'));          // nullconsole.log(get(obj, 'key.0.myArray.42'));     // nullvar childArray2 = [0,1,2]
var parentArray2 = [childArray2, childArray2]
var obj2 = {key: parentArray2}

console.log(get(obj2, 'key.1.0'));     // 0console.log(get(obj2, 'foo.1.0'));     // null

Solution 2:

With an invention of Object.prototype.getNestedValue() you can dynamically access deeply nested values through object properties and array indices. All you have to do is to provide the nested properties and indices dynamically as arguments in the correct order.

Object.prototype.getNestedValue = function(...a) {
  return a.length > 1 ? (this[a[0]] !== void0 && this[a[0]].getNestedValue(...a.slice(1))) : this[a[0]];
};

var arr = [{fox: [{turn:[857, 432]}]}, {sax: [{pana:[777, 987]}]}, {ton: [{joni:[123, 567]}]}, {piu: [{burn:[666, 37]}]}, {sia: [{foxy:[404, 696]}]}],
  myObj = { foo : 1, bar: { baz : 2 }, bee : 3 },
   arg1 = 3,
   arg2 = "piu",
   arg3 = 0,
   arg4 = "burn",
   arg5 = 1;

document.write(arr.getNestedValue(arg1,arg2,arg3,arg4,arg5));

Solution 3:

I would instead use an array of property names, which would allow you easy recursion.

But if you want to go back to your original pattern, you could still transform your expression into this array.

Have a look on this example:

var innerget = function(object, proparr) {
  if(proparr.length == 0) 
    return object;
  
  if(typeof object == "undefined" || object === null)
    return object;
  returninnerget(object[proparr.splice(0, 1)], proparr);
};

var get = function(object, expr) {
  var proparr = expr.replace(/\[/g, ".").replace(/\]/g, "").split(".");
  returninnerget(object, proparr);
}

var object = {
   key: [[1, 2, 3], [4, 5, 6]]  
};

document.write(innerget(object, ['key', 'key2', 2]) + "<br>");
document.write(innerget(object, ['key', 0, 2]) + "<br>");
document.write(get(object, "key[0][1]"));