Category: JavaScript

Sometimes, we want to select by object path with Lodash and JavaScript.

In this article, we’ll look at how to select by object path with Lodash and JavaScript.

How to select by object path with Lodash and JavaScript?

To select by object path with Lodash and JavaScript, we can use the get method.

For instance, we write:

const obj = {
  foo: 'bar',
  count: '3',
  counter: {
    count: '3',
  },
  baz: {
    test: "qux",
    tester: {
      name: "Ross"
    }
  }
};
const result = _.get(obj, 'baz.tester.name', 'defaultVal');
console.log(result)

We call get with the object we want to find the property value for, the path to the property value, and the default value returned when the property isn’t found respectively.

Therefore, result is 'Ross' since obj.baz.tester.name is 'Ross'.

Conclusion

To select by object path with Lodash and JavaScript, we can use the get method.

Sometimes, we want to get all keys of a deep object in JavaScript.

In this article, we’ll look at how to get all keys of a deep object in JavaScript.

How to get all keys of a deep object in JavaScript?

To get all keys of a deep object in JavaScript, we can recursive traverse the object to get the keys.

For instance, we write:

const obj = {
  foo: 'bar',
  count: '3',
  counter: {
    count: '3',
  },
  baz: {
    test: "qux",
    tester: {
      name: "Ross"
    }
  }
};

const objectDeepKeys = (obj, keys = []) => {
  for (const key of Object.keys(obj)) {
    keys.push(key)
    if (typeof obj[key] === 'object' && obj[key] !== null) {
      objectDeepKeys(obj[key], keys)
    }
  }
  return keys
}

console.log(objectDeepKeys(obj))

to define the objectDeepKeys function that takes the obj object to traverse and the array of keys.

In the function, we loop through each key we get from Object.keys with a for-of loop.

And in the loop, we have keys.push(key) to append the key to keys.

If obj[key] is an object and it’s not null, we call objectDeepKeys to do the same thing in the next level.

As a result, we see ['foo', 'count', 'counter', 'count', 'baz', 'test', 'tester', 'name'] logged.

Conclusion

To get all keys of a deep object in JavaScript, we can recursive traverse the object to get the keys.

Sometimes, we want to get the selected values of a multiple select element on change with JavaScript.

In this article, we’ll look at how to get the selected values of a multiple select element on change with JavaScript.

How to get the selected values of a multiple select element on change with JavaScript?

To get the selected values of a multiple select element on change with JavaScript, we can get all the options from the selectedOptions property of the select element.

For instance, we write:

<select multiple>
  <option value="apple">Apple</option>
  <option value="banana">Banana</option>
  <option value="mango">Mango</option>
  <option value="grape">Grape</option>
  <option value="watermelon">watermelon</option>
</select>

to add a multi-select element.

Then we write:

const select = document.querySelector('select')
select.onchange = (e) => {
  const selectedVals = [...e.target.selectedOptions].map(o => o.value)
  console.log(selectedVals)
}

to select the select element with querySelector.

We then set the select.onchange property to a function that gets all the selected options.

To do this, we get all the selected options with e.target.selectedOptions.

And then we spread them into an array and call map with a callback that returns the value from each selected option.

Conclusion

To get the selected values of a multiple select element on change with JavaScript, we can get all the options from the selectedOptions property of the select element.

Sometimes, we want to add an array to two-dimensional array with JavaScript.

In this article, we’ll look at how to add an array to two-dimensional array with JavaScript.

How to add an array to two-dimensional array with JavaScript?

To add an array to two-dimensional array with JavaScript, we can use the array push method.

For instance, we write:

const arr = [
  [1, 2, 3],
  [4, 5, 6],
];

arr.push([7, 8, 9]);
console.log(arr)

to call arr.push to append a new array to arr.

Therefore, arr is:

[
  [
    1,
    2,
    3
  ],
  [
    4,
    5,
    6
  ],
  [
    7,
    8,
    9
  ]
]

Conclusion

To add an array to two-dimensional array with JavaScript, we can use the array push method.