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How to call function from it name stored in a string using JavaScript ?

Last Updated : 04 Nov, 2025
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In this article, we will call a function from the string stored in a variable. There are two methods to call a function from a string stored in a variable.

Note: The eval() method is older and is deprecated

[Approach 1]: Using the window object

The window object in HTML 5 references the current window and all items contained in it. Hence we can use it to run a function in a string along with parameters to the function.

html 
<h1 style="color: green">
    GeeksforGeeks
</h1>

<b>
    How to call function from string stored
    in a variable using JavaScript
</b>

<p>
    Click on the button to call the
    function in the string
</p>

<p class="example">
    GeeksforGeeks is a computer
    science portal.
</p>

<button onclick="evaluateFunction()">
    Click here
</button>

<script type="text/javascript">
    function changeColor(color) {
        document.querySelector('.example').style
            = `color: ${color}`;
    }
    
    function evaluateFunction() {
        stringFunction = "changeColor";
        param = 'green';
        window[stringFunction](param);
    }
</script>

Syntax:

window[functionName](parameters)

[Approach 2]: Using the eval() method

  • The other method that can be used is the eval() method.
  • The string that may be passed on to the function may include a JavaScript expression, statement, or a sequence of statements.
  • It can also have variables and properties of existing objects.
  • The only problem with this method is that it is considered unsafe and may not be supported by newer browsers.
html 
<h1 style="color: green">
    GeeksforGeeks
</h1>

<b>
    How to call function from string stored
    in a variable using JavaScript
</b>

<p>
    Click on the button to call the
    function in the string
</p>

<p class="example">
    GeeksforGeeks is a computer
    science portal.
</p>

<button onclick="evaluateFunction()">
    Click here
</button>

<script type="text/javascript">
    function changeColor(color) {
        document.querySelector('.example').style
                = `color: ${color}`;
    }
        
    function evaluateFunction() {
        stringFunction = "changeColor('green')";
        eval(stringFunction);
    }
</script>



S

sayantanm19
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