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How to add key/value pair to a JavaScript object ?

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  • Last Updated : 03 Jan, 2023
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In order to add key/value pair to a JavaScript object, Either we use dot notation or square bracket notation. Both methods are widely accepted. 

Example 1: This example adds {“nextFavColor” : “red”} to the GFG_p object by using dot notation

html




<h1 style="color:green;">
    GeeksForGeeks
</h1>
 
<p id="GFG_up" style="color:red;"></p>
 
<button onclick="Geeks()">
    Click to add
</button>
 
<p id="GFG_down" style="color:green;"></p>
 
<script>
    var GFG_p = {fName:"Geeks", lName:"forGeeks",
                age:100, favColor:"green"};
    var p_up = document.getElementById("GFG_up");
    var p_down = document.getElementById("GFG_down");
    p_up.innerHTML = JSON.stringify(GFG_p);
      
    function Geeks() {
        GFG_p.nextFavColor = "Red";
        p_down.innerHTML = JSON.stringify(GFG_p);    
    }
</script>

Output:

 

Example 2: This example adds {“thirdFavColor” : “blue”} to the GFG_p object by using square bracket notation

html




<h1 style="color:green;">
    GeeksforGeeks
</h1>
  
<p id="GFG_up" style="color:blue;"></p>
  
<button onclick="Geeks()">
    Click to add
</button>
  
<p id="GFG_down" style="color:green;"></p>
  
<script>
    var GFG_p = {fName:"Geeks", lName:"forGeeks",
                age:100, favColor:"green"};
    var p_up = document.getElementById("GFG_up");
    var p_down = document.getElementById("GFG_down");
    p_up.innerHTML = JSON.stringify(GFG_p);
      
    function Geeks() {
        GFG_p["thirdFavColor"] = "blue";
        p_down.innerHTML = JSON.stringify(GFG_p);    
    }
</script>

Output:

 


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