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How to check whether an object exists in javascript ?

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  • Last Updated : 23 Jan, 2023
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An object can be used to check if it exists using 2 approaches: 

Method 1: Using the typeof operator The typeof operator returns the type of the variable on which it is called as a string. The return string for any object that does not exist is “undefined”. This can be used to check if an object exists or not, as a non-existing object will always return “undefined”. 

Syntax: 

if (typeof objectToBeTested != "undefined") 
    // object exists 
else
    // object does not exist 

Example: 

HTML




<h1 style="color: green">
    GeeksforGeeks
</h1>
<b>How to check whether an
    object exists in javascript</b>
  
<p>Click on the button to
    check if the object exists</p>
  
<p>Output for existing object:
    <span class="outputExist"></span>
</p>
<p>Output for non existing object:
    <span class="outputNonExist"></span>
</p>
  
<button onclick="checkObjectExists()">
    Click here
</button>
<script type="text/javascript">
    function checkObjectExists() { 
        // create an existing object for comparison 
        let existingObject = {}; 
      
        if (typeof existingObject != "undefined") { 
            ans = true; 
        } else { 
            ans = false
        
      
        document.querySelector( 
        '.outputExist').textContent = ans; 
      
        if (typeof nonExistingObject != "undefined") { 
            ans = true; 
        } else { 
            ans = false; 
        
      
        document.querySelector( 
        '.outputNonExist').textContent = ans; 
    
</script>

Output:

How to check whether an object exists in javascript ?

How to check whether an object exists in javascript ?

Method 2: Using a try-catch statement to catch a Reference error Accessing a non-existing object will always throw a Reference error. A try-catch block can be used to determine this error. Any random property of the element can be accessed for this error to be thrown. 

Syntax: 

try {
    objectToBeTested.prop;
    // object exists
}
catch {
    // object does not exist
}

Example: 

javascript




<h1 style="color: green">
    GeeksforGeeks
</h1>
<b>How to check whether an
    object exists in javascript</b>
  
<p>Click on the button to check
    if the object exists</p>
<p>Output for existing object:
    <span class="outputExist"></span>
</p>
  
<p>Output for non existing object:
    <span class="outputNonExist"></span>
</p>
  
<button onclick="checkObjectExists()">Click here</button>
<script type="text/javascript">
    function checkObjectExists() { 
      
        // create an existing object for comparison 
        let existingObject = {}; 
      
        try
            // accessing a random property 
            existingObject.prop; 
            ans = true
        } catch
            ans = false
        
      
        document.querySelector( 
        '.outputExist').textContent = ans; 
      
        try
            // accessing a random property 
            nonExistingObject.prop; 
            ans = true
        } catch
            ans = false
        
      
        document.querySelector( 
        '.outputNonExist').textContent = ans; 
      
    
</script>

Output:

How to check whether an object exists in javascript ?

How to check whether an object exists in javascript ?


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