There are many cases where you need to check the table’s existence before writing any logic. For static tables, it is not necessary to check their existence, but for dynamic tables, it’s a mandatory job to check their existence first to keep away from uncertain mistakes.
In this blog post, “How to Check if a Table Exists in JavaScript?” we are going to describe all available strategies together with their proper use cases to test if a table exists or not in JavaScript. We will offer code examples and code explanations as well.
Table of Contents
5 Methods to Explain – How to Check if a Table Exists in JavaScript?
There are a lot of methods to check whether a table exists or not in your HTML page using JavaScript. Among those, we are going to cover four basic methods below:
- Using getElementById
- Using querySelector
- Using getElementsByTagName
- Using querySelectorAll
- Using getElementsByClassName
1. Using getElementById
The table that you are going to check, you need to know whether this HTML table contains an ID or not. If yes, then this method is the best method to check table existence in runtime:
Code example
<!DOCTYPE html>
<html>
<head>
<title>Check Table Example</title>
</head>
<body>
<table id="myTable">
<tr>
<td>Row 1, Cell 1</td>
<td>Row 1, Cell 2</td>
</tr>
</table>
<script>
function checkTableById() {
var table = document.getElementById("myTable");
if (table) {
console.log("Table exists!");
} else {
console.log("Table does not exist.");
}
}
checkTableById();
</script>
</body>
</html>output
2. Using querySelector
This method uses a CSS selector to find the table. It is more flexible than getElementById. Because if you don’t know the ID of the table that you are looking for, you can select the table with its associated class name. Be mindful that the querySelector method always returns the first matched element, not all.
Code Example
<!DOCTYPE html>
<html>
<head>
<title>Check Table Example</title>
</head>
<body>
<table class="myTableClass">
<tr>
<td>Row 1, Cell 1</td>
<td>Row 1, Cell 2</td>
</tr>
</table>
<script>
function checkTableBySelector() {
var table = document.querySelector(".myTableClass");
if (table) {
console.log("Table exists!");
} else {
console.log("Table does not exist.");
}
}
checkTableBySelector();
</script>
</body>
</html>3. Using getElementsByTagName
If you don’t know table IDs or class names but you want to check the presence of some or all tables on your web page, then use the selector getElementsByTagName. Using getElementsByTagName, you can identify and loop through each and every table on your page. Look at the below example:
code example
<!DOCTYPE html>
<html>
<head>
<title>Check Table Example</title>
</head>
<body>
<table>
<tr>
<td>Row 1, Cell 1</td>
<td>Row 1, Cell 2</td>
</tr>
</table>
<script>
function checkTableByTagName() {
var tables = document.getElementsByTagName("table");
if (tables.length > 0) {
console.log("Table exists!");
} else {
console.log("Table does not exist.");
}
}
checkTableByTagName();
</script>
</body>
</html>4. Using querySelectorAll
This method uses a CSS selector to find the table(s). It is more useful than getElementById and querySelector. GetElementById always selects only one table at a time, as you could offer one ID at a time.
Though querySelector can take a class name as a parameter instead of an ID, this method returns the first element that matches the provided class name.
If you need to test multiple tables, then querySelectorAll is the best solution for you because it returns all matched table elements, in contrast to querySelector.
code example
<!DOCTYPE html>
<html>
<head>
<title>Check Table Example</title>
</head>
<body>
<table class="myTableClass">
<tr>
<td>Row 1, Cell 1</td>
<td>Row 1, Cell 2</td>
</tr>
</table>
<table class="myTableClass2">
<tr>
<td>Row 1, Cell 1</td>
<td>Row 1, Cell 2</td>
</tr>
</table>
<table class="myTableClass">
<tr>
<td>Row 1, Cell 1</td>
<td>Row 1, Cell 2</td>
</tr>
</table>
<script>
function checkTableBySelectorAll() {
var tables = document.querySelectorAll(".myTableClass");
if (tables.length > 0) {
console.log("Table exists!");
console.log("No of Table: "+tables.length);
} else {
console.log("Table does not exist.");
}
}
checkTableBySelectorAll();
</script>
</body>
</html>output
2nd table not selected as it’s classname “myTableClass2” does not match.
5. Using getElementsByClassName
The getElementsByClassName() method returns an HTML collection. You can supply more than one class name to exactly identify your desired table or tables.
code example
<!DOCTYPE html>
<html>
<head>
<title>Check Table Example</title>
</head>
<body>
<table class="myTableClass stylex">
<tr>
<td>Row 1, Cell 1</td>
<td>Row 1, Cell 2</td>
</tr>
</table>
<table class="myTableClass styley">
<tr>
<td>Row 1, Cell 1</td>
<td>Row 1, Cell 2</td>
</tr>
</table>
<table class="myTableClass stylez">
<tr>
<td>Row 1, Cell 1</td>
<td>Row 1, Cell 2</td>
</tr>
</table>
<script>
function checkTableBySelectorAll() {
// document.getElementsByClassName("myTableClass stylex styley") return 0
// document.getElementsByClassName("myTableClass stylex") return 1
// document.getElementsByClassName("myTableClass styley") return 1
// document.getElementsByClassName("myTableClass") return 3
var tables = document.getElementsByClassName("myTableClass styley");
if (tables.length > 0) {
console.log("Table exists! No of Table: "+tables.length);
} else {
console.log("Table does not exist.");
}
}
checkTableBySelectorAll();
</script>
</body>
</html>output
Comparison Table
Table: comparing the different methods to check whether a table exists or not using JavaScript:
| Method | Description | Use case |
|---|---|---|
| getElementById | Checks by ID | If you know the table’s ID. |
| querySelector | Checks by CSS selector | If you know the class name. |
| getElementsByTagName | Checks for any <table> elements | If you don’t know ID and class name. |
| querySelectorAll | Checks for all matching selectors | If you need to select multiple table. |
| getElementsByClassName | Checks for all matching class names | If you need to select all tables with a combination of class names. |
Useful Tips
- Use Specific IDs: When possible, use unique IDs for your tables. This makes it less complicated to choose them with getElementById.
- CSS Selectors for Flexibility: Use querySelector and querySelectorAll for more complex queries.
- Check for Multiple Tables: If you want to check multiple tables, querySelectorAll and getElementsByClassName are the essential methods.
Conclusion
In this blog post, we explain 5 different methods to check whether a table present or not on your page using JavaScript. These methods clearly provide the use of getElementById, querySelector, getElementsByTagName, querySelectorAll, and getElementsByClassName. Each method has its own use case and benefits. Apply these methods based on your needs.
Remember to choose the best method that suits your specific goals. Whether you want to check for a table via ID, CSS class, or tag name on the web page, all methods will help you efficiently.
How to Check if a Table Exists in JavaScript? The answer is: By following those above methods, you can implement your JavaScript code and ensure that it runs smoothly by avoiding errors related to non-existent tables. Happy coding!
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