The simplest way to merge JSON arrays usning JQuery is to use the concat function.
var json1 = [{id: 1, name: "one"}];
var json2 = [{id: 2, name: "two"}, {id: 3, name: "three"}];
var finalObj = json1.concat(json2);
Here finalObj will contain an array of 3 objects:
[{id: 1, name: “one”},{id: 2, name: “two”}, {id: 3, name: “three”}]
JQuery Check if Element Exists using this simple piece of code. To check this in the current page, we need to check the length of the element returned by the JQuery selector, if it returns you something then the element must exists otherwise no.
if( $('#EleSelector').length ) { // use this if you are using id, replace EleSelector with the id
// it exists
}
if( $(‘.EleSelector’).length ) { // use this if you are using class, replace EleSelector with the id
// it exists
}
In case of plain javascript try this:
//you can use it for more advanced selectors
if(document.querySelectorAll("#EleSelector").length){}
if(document.querySelector("#EleSelector")){}
//you can use it if your selector has only an Id attribute
if(document.getElementById("EleSelector")){}
For a check box with the id “checkbox”, here is how to check if its checked:
$('#checkbox').is(':checked'); // Returns True if checked else False
JavaScript has two sets of equality operators: === and ==. They mostly work exactly the same ie, if the operands are of the same type and have the same value, then === produces true & so does ==. But if the operands are of different types, then === produces false & == says true. The simplest reason is that == is also a type converter.
Here are some examples of === & == in action:
true == 1 // true
true === 1 // false, because they are of a different type
1 == "1" // true, automatic type conversion for value only
1 === "1" // false, because they are of a different type
null == undefined // true
null === undefined // false
== is also notoriously inconsistent. See the below examples:
'' == '0' // false
0 == '' // true
0 == '0' // true
false == 'false' // false
false == '0' // true
false == undefined // false
false == null // false
null == undefined // true
' \t\r\n ' == 0 // true
Best practice is to avoid == and use === consistently in your code.
Update (2025): This guide has been updated with modern ES6+ methods and troubleshooting FAQs to ensure it works with the latest web standards and frameworks.
Iterating through dropdown (select) options is a fundamental task in web development. Whether you are validating a form, dynamically filtering data, or syncing UI states, knowing how to efficiently loop through a <select> element’s options is essential for a smooth user experience.
In this guide, we will cover the modern ES6+ way, the traditional approach, and the jQuery method.
The most efficient and readable way to handle this today is by converting the HTMLOptionsCollection into an array and using the forEach method. This is the standard in modern frameworks like React, Vue, or Vanilla JS projects.
JavaScript
// Get the dropdown by ID
const dropdown = document.getElementById("dropdownlist");
// Convert options to an Array and iterate
Array.from(dropdown.options).forEach((option) => {
console.log("Text:", option.text, "Value:", option.value);
// Add your custom logic or operations here
});
If you need to support legacy browsers (like very old versions of IE) or prefer the standard for loop, use the code below. It is highly performant as it avoids creating an array copy.
JavaScript
var x = document.getElementById("dropdownlist");
for (var i = 0; i < x.options.length; i++) {
console.log("Value: " + x.options[i].value);
// Perform operations based on each option
}
If your project is already utilizing the jQuery library, the .each() method provides a very concise and readable syntax for targeting child options.
JavaScript
$("#dropdownlist > option").each(function() {
console.log("Text: " + this.text + " | Value: " + this.value);
// Add your operations here
});
| Method | Best For | Complexity |
|---|---|---|
| ES6 Array.from() | Modern Web Apps / Clean Code | Low |
Standard for loop | High Performance / Legacy Support | Medium |
jQuery .each() | Projects already using jQuery | Low |
How do I select a specific value while iterating?
You can add a simple conditional check inside your loop. For example: if (option.value === "target") { option.selected = true; }
How do I get the total count of options in a dropdown?
You can simply access the length property: document.getElementById("dropdownlist").options.length;
Can I iterate through a dropdown without using an ID?
Yes, you can use document.querySelector('select') or document.getElementsByClassName('your-class') to target the element without an ID.