2 days ago

How can I substitute the value of a nested object provided that the key exists?

Here's my revised paragraph: I'm trying to loop through an array that contains nested objects and replace the value of an object's key if it exists, then break out of the loop. If the key doesn't exist in any of the objects, I want to add a new object to the array and print the updated array. Unfortunately, my code below isn't working. Can you tell me what went wrong and how to fix it? Thank you!

Here's the array:

const x = [
  { "s": "23", "t": "41" },
  { "e": "29", "t": "87" }

for (let i = 0; i < x.length; i++) {
  if ("d" in x[i]) {
    x[i]["t"] = "21";
  } else if (i === x.length - 1) {
    x.push({ "d": "22", "t": "77" });
Let me know if you have any questions about this code or how it works!
2 days ago
Verified Answer
The issue with the code provided is that it is checking for the key "d" in the objects but no object in the array has that key. To fix this, you should check for the key that you are actually looking for. Additionally, the else-if statement should be modified to check if the loop has reached the end of the array and not just if it's the last object in the array. Here's the corrected code:
x = [{
  "s": "23",
  "t": "41"
}, {
  "e": "29",
  "t": "87"

var key = "s";
var newValue = "55";
var keyExists = false;

for (var i = 0; i < x.length; i++) {
  if (key in x[i]) {
    x[i][key] = newValue;
    keyExists = true;

if (!keyExists) {
    [key]: newValue,
    "t": "77"

In this code, you can specify the key you want to check for using the key variable and the new value you want to replace it with using the newValue variable. The keyExists variable is used to track if the key exists in any object in the array. If it doesn't, a new object is appended with the specified key and value using computed property names.