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How [ ] is converted to String in JavaScript?

HTML Javascript Programming Scripts

In JavaScript, an empty array [] converts to an empty string "" when converted to a string. This happens through JavaScript's automatic type conversion or by using explicit conversion methods.

Using String() Method

The String() method explicitly converts any value to a string:

<!DOCTYPE html>
<html>
<body>
    <p>Convert [] to String</p>
    <script>
        var myVal = [];
        document.write("String: " + String(myVal));
        document.write("<br>Type: " + typeof String(myVal));
    </script>
</body>
</html>

String: 
Type: string

Using toString() Method

Arrays have a built-in toString() method that converts them to strings:

<!DOCTYPE html>
<html>
<body>
    <script>
        var emptyArray = [];
        var arrayWithItems = [1, 2, 3];
        
        document.write("Empty array: '" + emptyArray.toString() + "'<br>");
        document.write("Array with items: '" + arrayWithItems.toString() + "'");
    </script>
</body>
</html>

Empty array: ''
Array with items: '1,2,3'

Automatic Type Conversion

JavaScript automatically converts arrays to strings when used in string contexts:

<!DOCTYPE html>
<html>
<body>
    <script>
        var arr = [];
        document.write("Concatenation: '" + arr + "'<br>");
        document.write("Template literal: '" + `${arr}` + "'");
    </script>
</body>
</html>

Concatenation: ''
Template literal: ''

Comparison of Methods

Method	Result for []	Works with null/undefined?
`String([])`	`""`	Yes
`[].toString()`	`""`	No (throws error)
`[] + ""`	`""`	Yes

Conclusion

An empty array [] converts to an empty string "" in JavaScript. Use String() for explicit conversion or rely on automatic conversion in string contexts.

Swarali Sree

Updated on: 2026-03-15T23:18:59+05:30

223 Views

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