How to check if a string is html or not using JavaScript?

0 0 1 minute read

The task is to validate whether the given string is valid HTML or not using JavaScript. we’re going to discuss a few techniques.

Approach

Get the HTML string into a variable.
Create a RegExp which checks for the validation.
RegExp should follow the rules of creating an HTML document.

Example 1: In this example, a regexp is created and it is validating the HTML string as valid.

html

<h1 style="color:green;" id="h1"> 
    zambiatek 
</h1> 
<p id="GFG_UP"> 
</p> 
<button onclick="GFG_Fun()"> 
    click here 
</button> 
<p id="GFG_DOWN"> 
</p> 
<script> 
    var up = document.getElementById('GFG_UP'); 
    var str1 = '<div>GeeksForGeeks</div>'; 
    var str = '<div>GeeksForGeeks</div>'; 
      
    up.innerHTML = "Click on the button to check "+ 
    "for the valid HTML.<br> String - " + str1; 
      
    var down = document.getElementById('GFG_DOWN'); 
      
    function GFG_Fun() { 
        down.innerHTML = 
    /<(?=.*? .*?\/ ?>|br|hr|input|!--|wbr)[a-z]+.*?>|<([a-z]+).*?<\/\1>/i.test(str); 
    } 
</script>

Output:

How to check if a string is html or not using JavaScript?

Example 2: In this example, Here also, A regexp is created and it is validating the HTML string as invalid.

html

<h1 style="color:green;" id="h1"> 
    zambiatek 
</h1> 
<p id="GFG_UP"> 
</p> 
<button onclick="GFG_Fun()"> 
    click here 
</button> 
<p id="GFG_DOWN"> 
</p> 
<script> 
    var up = document.getElementById('GFG_UP'); 
    var str1 = '<div>GeeksForGeeks</dv>'; 
    var str = '<div>GeeksForGeeks</dv>'; 
      
    up.innerHTML = "Click on the button to check "+ 
    "for the valid HTML.<br> String - " + str1; 
      
    var down = document.getElementById('GFG_DOWN'); 
      
    function GFG_Fun() { 
        down.innerHTML = 
    /<([A-Za-z][A-Za-z0-9]*)\b[^>]*>(.*?)<\/\1>/.test(str); 
    } 
</script>

Output:

How to check if a string is html or not using JavaScript?

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