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JavaScript Function Parameters

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  • Difficulty Level : Medium
  • Last Updated : 26 Dec, 2022
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The Javascript Function Parameters are the names that are defined in the function definition and real values passed to the function in the function definition are known as arguments. 

Syntax: 

function Name(paramet1, paramet2, paramet3,...) {
    // Statements
}

Parameter Rules: 

  • There is no need to specify the data type for parameters in JavaScript function definitions.
  • It does not perform type-checking based on the passed-in JavaScript functions.
  • It does not check the number of received arguments.

Parameters: 

  • Name: It is used to specify the name of the function.
  • Arguments: It is provided in the argument field of the function.

Example: This example uses JavaScript function parameters and finds the largest number. 

html




<body style="text-align:center;">
    <h2 style="color:green">GeeksForGeeks</h2>
    <h4>Function Parameters and Arguments</h4>
  
    <p>Finding the largest number : (4, 50, 6)</p>
  
    <p id="geeks"></p>
  
    <script>
        function GFG( var1, var2, var3 ) {
            if( var1 > var2 ) {
                if( var1 > var3 ) {
                    return var1;
                }
                else {
                    return var3;
                }
            }
            else {
                if( var2 > var3 ) {
                    return var2;
                }
                else {
                    return var3;
                }
            }
        }
        document.getElementById("geeks").innerHTML
                = GFG(4, 50, 6);
    </script>
</body>

Output: 

 

Defaults Parameter: The default parameters are used to initialize the named parameters with default values in case, when no value or undefined is passed. 

Syntax: 

function Name(paramet1 = value1, paramet2 = value2 .. .) {
    // statements
}

Example: This example uses default parameters and performs the multiplication of numbers. 

html




<body style="text-align:center;">
    <h2 style="color:green">GeeksForGeeks</h2>
    <h4>Function Parameters and Arguments</h4>
  
    <p>GFG Function multiply : </p>
  
    <p id="geeks"></p>
  
    <script>
        function GFG(num1, num2 = 2) {
            return num1 * num2;
        }
          
        document.getElementById("geeks").innerHTML
                = GFG(4);
    </script>
</body>

Output: 

 

Arguments Object: The arguments objects are inbuilt objects in JavaScript functions. In all non-arrow functions, the arguments object is a local variable. Analyze the arguments inside the function by using its arguments object. 

Example: This example uses argument objects as parameters and finds the largest of numbers. 

html




<body style="text-align:center;">
    <h2 style="color: green">GeeksForGeeks</h2>
    <h4>Function Parameters and Arguments</h4>
  
    <p>
        Finding the largest number in :
        (10, 12, 500, 5, 440, 45)
    </p>
  
    <p id="geeks"></p>
  
    <script>
        function GFG() {
            var i;
            var maxnum = -Infinity;
            for(i = 0; i < arguments.length; i++) {
                if (arguments[i] > maxnum) {
                    maxnum = arguments[i];
                }
            }
            return maxnum;
        }
        document.getElementById("geeks").innerHTML
                = GFG(10, 12, 500, 5, 440, 45);
    </script>
</body>

Output: 

 

Arguments Pass by Value: In a function call, the parameters are called as arguments. The pass-by value sends the value of the variable to the function. It does not send the address of the variable. If the function changes the value of arguments then it does not affect the original value. 

Example: This example demonstrates the above-used approach.

html




<body style="text-align:center;">
    <h1 style="color:green">GeeksForGeeks</h1>
    <h4>Arguments are Passed by Value</h4>
  
    <p id="geeks"></p>
  
    <!-- Script to illustrate the use of arguments
        passed by value -->
    <script>
        /* Function definition */
        function GeeksForGeeks(var1, var2) {
            document.write("Inside the GeeksForGeeks function");
            document.write('<br/>');
              
            var1 = 100;
            var2 = 200;
              
            /* Display the value of variable inside function */
            document.write("var1 =" + var1 +" var2 =" +var2);
            document.write('<br/>');
        }
          
        var1 = 10;
        var2 = 20;
          
        /* The value of variable before Function call */
        document.write("Before function calling");
        document.write('<br/>');
          
        document.write("var1 =" + var1 +" var2 =" +var2);
        document.write('<br/>');
          
        /* Function call */
        GeeksForGeeks(var1,var2);
          
        /* The value of variable after Function call */
        document.write("After function calling");
        document.write('<br/>');
          
        document.write("var1 =" + var1 +" var2 =" +var2);
        document.write('<br/>');
    </script>
</body>

Output: 

 

Objects passed by Reference: In Objects Pass by Reference, passing the address of the variable instead of the value as the argument to call the Function. If we change the value of the variable inside the function then it will affect outside function variables. 

Example: This example demonstrates the above-used approach.

html




<body style="text-align:center;">
    <h1 style="color:green">GeeksForGeeks</h1>
    <h4>Arguments are Passed by Value</h4>
  
    <p id="geeks"></p>
  
    <script>
        function GeeksForGeeks(varObj) {
            document.write("Inside GeeksForGeeks function");
            document.write('<br/>');
            varObj.a = 100;
            document.write(varObj.a);
            document.write('<br/>');
        }
          
        // Create object
        varObj = {a:1};
          
        /* Display value of object before function call */
        document.write("Before function calling");
        document.write('<br/>');
        document.write(varObj.a);
        document.write('<br/>');
          
        /* Function calling */
        GeeksForGeeks(varObj)
          
        /* Display value of object after function call */
        document.write("After function calling");
        document.write('<br/>');
        document.write(varObj.a);
    </script>
</body>

Output: 

 


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